Stratton sat on one of the team boxes studying a chart. He glanced up as rain began to pound at the glass portholes. The storm would give the team good cover. But if it grew too powerful it would affect their ability actually to reach the target.

He had serious misgivings about the approach to the platform. And if he was concerned, why wasn’t London? It was part of the reason he still could not fully accept that the operation had been allowed to proceed with the scientists. Surely Jervis knew these clowns were not up to a task. Granted it was only a surveillance job, and if carried out procedurally they should never come into contact with the enemy. But it was still high risk and, even though London was not averse to taking chances, they were not usually of this nature.

Stratton got to his feet and, keeping a hand against the bulkhead, made his way to the front of the cabin. The chopper was buffeting heavily, as much as he could ever remember having experienced - with a live pilot still in control of the sticks, that was. He put on the headphones and asked for the operations room to recalculate the tidal speed and direction from the drop-off point. Heavy storms such as this one - which was only going to get worse - had a habit of shifting such things. The fast currents in the North Sea moved in long sweeping curves. If the drop-off was not accurately calculated they could miss the platform despite the speed the sub could reach.

Five minutes later the drop-off latitude and longitude were relayed back to him. Stratton gathered the team to brief them. Jackson, as it turned out, was not only a helicopter and fixed-wing pilot. Mansfield had sent him on a mini-sub operator’s training course in Norfolk, Virginia, at the beginning of the year. Stratton wondered how far the MI16 boss’s ambitions extended.

Stratton explained how the team would manoeuvre in and out of the tight-fitting vessel and how they should conduct themselves while it was under the water. When the briefing was complete the team climbed into lightweight dry-bags, tightened harnesses and clipped on fins, masks and the small transfer air bottles they would need when they were not connected to the sub’s breathing system. Binning strapped the surveillance device securely to his side and jumped up and down a few times to ensure it was solidly attached. He had clearly seen it done on some kind of military training film since it did not quite apply to a dive operation. At least he was keen.

Stratton allowed the team to carry pistols but insisted that he alone would have a sub-machine gun, a silenced H&K to go with his pistol and two stun grenades. He neglected to mention during the briefing his own private operation: the only points he covered were the planting of the surveillance device and the move to the rendezvous pick-up location. The way he questioned Jason on all details of that last phase of the operation ought to have suggested something to them. In truth, it was blatantly obvious that he wouldn’t be able to get Jordan away from the oil platform on the submarine, assuming of course that he could rescue him at all. As far as he could see the only option he had was to secure one of the platform’s lifeboats: a broad enough plan - if it could be called that - for him not to have to think of it any more. First he had to locate Jordan, then separate him from the hijackers. He couldn’t do much planning for that. Every stage would be a process of discovery, assessment, action and follow-on. Another reason to put it to one side.

With everyone fully rigged Stratton put them through a dry drill on the submarine, covering signals between cockpit and cabin, switching between the sub’s breathing system and individual air bottles, and climbing in and out of the vessel. He questioned them on the details of every phase of the operation, the sequence of events, who would be doing what and when. He finished by explaining emergency contingency plans for anyone failing to climb the platform or falling off it - if they found themselves alone and unattached in the water their best bet would be simply to flow with the tide away from the rig and when well out of range initiate the emergency strobe lights and the SARBE emergency radio beacon that they each carried. Even in a severe storm, as long as they remained afloat there was a high chance of rescue since a good portion of the navy and air force was concentrated in the area.

Stratton did not go into great detail about climbing the platform. That would depend on their fitness and their ability to manage a caving ladder while in a dry-bag and carrying some equipment. They couldn’t practise that in the Chinook - it was going to have to be done on the job.

He introduced them to the air-powered grapnel launcher, explaining how he planned to use it and how it was stowed and retrieved from inside the sub. He then secured it in the mini-sub’s cabin along with the rolls of caving ladders, lines and hooks. He concluded the briefing just in time. The crewman had left the cockpit and was making his way over to them, grabbing hold of whatever part of the craft he could as it yawed from one side to the other. ‘We’ll be at the drop point in five minutes!’ he shouted.

Stratton acknowledged him and faced the others. ‘Does anyone have any questions about any phase of the mission?’

‘How long do we give you?’ Jason asked. ‘I refer to your private mission.’

‘Don’t forget that’s what got you this far,’ Stratton replied, a little testily.

‘And I appreciate it,’ Jason said. ‘But the question remains.’

‘Soon as you’ve placed the device get on your way.’

‘How are you going to get away with Mackay?’ Jason said.

‘Don’t worry about that. You have your task, you have a sound plan to carry it out and you have your exfiltration options. Concentrate on them.’

The white lights went off in the cabin, to be replaced by dim red ones that barely illuminated the cramped space. The whine of an electric motor filled the air and the rear ramp began to open. A blast of wind and rain came in through the widening opening, over the top and sides of the ramp as if it was impatient to explore inside. The noise of the rotors increased, their rhythmic beating coming in on the wind. When they looked out it was pure black, impossible to see where the sky ended and the ocean began. A sheet of lightning cut through the dark and for a few seconds they saw what lay outside. The helicopter pushed on into the broiling storm. In the cockpit the faces of both pilots glowed green beneath the night-vision goggles they wore.

With the ramp locked open at a steep angle towards the water, the helicopter descended. Now they could see the sea. Every toppling white wave of it. Stratton put in earphones, tucked the loose cable behind his throat microphone and pulled on his neoprene hood to help keep it all in place. He checked that the transfer breather bottle was secure and tested his dry-suit’s inflation. He looped the mouthpiece strap of his face mask over his head and tested the equipment secured to his body, including the SMG that fitted across his waist.

The rest of the team took this as their cue and pulled on their hoods, nervousness rippling between them as the seconds passed. Stratton had done this many times before. The others had never even imagined this level of adventure. They stood inside a yawing metal crate held in the air by a couple of rotors on the ends of struggling petrol-driven turbines. About to jump into the void. Into a small submarine. Into a perfect North Sea storm.

Stratton had seen their fear a thousand times before in the eyes of young soldiers going into battle for the first time. He had been assessing them from the moment they all truly knew the task would happen. He had studied their eyes as he briefed them. He knew that none of them could really comprehend the threat of confronting the armed hijackers. They wouldn’t be able to get beyond the dangers of the journey to the platform and the subsequent climb. He couldn’t blame them: this type of manoeuvre was one of the most perilous tasks the SBS undertook, even without the threat at the other end of an enemy with lethal intent. He suspected that despite agreeing to come on the jolly old operation they were now filled with doubt as to whether they could actually pull it off.

Jason hid his fears better than the others and would probably be the first to overcome them. He had to be frightened in some way. He wouldn’t be normal otherwise. But his eyes gave nothing away, except for an occasional look at Stratton as though to assess the operative’s nerve. No doubt the man knew that his ambitious plans for MI16’s operational future hung in the balance.

Binning looked nervous but he seemed to be driven by something, as if his life depended on getting onto the platform. Stratton suspected an element of competion with his boss. And perhaps for more than just his job, judging by the way he eyed Rowena.

Smithy was the main concern. He seemed on the verge of snapping, no longer able to make a decision on his own, watching to see what the others were doing before he took the step himself. He could become a liability - if he didn’t back out at the last minute. Stratton wondered what effect it would have on the team’s morale if he ordered the man to stand down. Jason must surely be aware of the problem. The operative decided not to step in: too many variables to worry about.

Jackson appeared to be in control of his nerves, cool enough. Stratton had the distinct feeling that the man had some previous military experience. He’d let slip a fair amount of jargon, especially when he’d been talking to the crewman, and he knew his way around the equipment. With a faulty torch from the equipment box, for instance, he’d immediately unscrewed the base, removed the first battery, reversed it and replaced the base - and it had worked. A classic soldier’s trick to prevent a torch from accidentally coming on.

Rowena was the interesting one. She was nervous but didn’t allow it to get in her way. She didn’t seem to share Jason’s enthusiasm or even agree with MI16’s taking the task on.Yet she’d stayed with the team. Stratton doubted that she was there just to be alongside her lover. She was far too mature for that. He couldn’t see what was keeping her on track. Stratton assumed the affair was a secret between them. They hardly acknowledged each other when there was anyone about. If he hadn’t seen them embrace so passionately he wouldn’t have guessed it. He wondered if Binning knew. If not, that helped to explain his sometimes overt interest in her.

‘Stratton!’ a voice shouted from the back of the cabin. George gave the team leader the thumbs-up and followed this gesture by raising one finger. They had a minute before the release.

Stratton stood at the top of the ramp and looked down at the rolling black water. The peaks were rising to foaming white plumes and the swell was enormous, fifty to sixty feet. In the right gear you could float on the surface, rising and falling from peak to trough. With breathing apparatus you could slip beneath the surface and the storm would disappear. All well and good. The dangers came when a person in such a heavy sea came into contact with a rigid mass, such as a quayside, a ship, a submarine, or an oil platform. Bodies had a tendency to get slammed against surfaces. Like an egg dropping onto a stone floor. Nothing about the next few hours was going to be easy.

Stratton pulled on his fins and tightened the straps. ‘Close up,’ he shouted, tightening the thin neoprene gloves around his fingers.

The team shuffled forward in their fins.

‘Stratton,’ George shouted, holding one side of his headset tight against his ear. ‘You have to go! Charlie’s having trouble holding it. Says we’ll all bloody join you if we don’t dump this lot and get out of here.’

Stratton gave him a firm thumbs-up and the crewman ducked down to remove the blocks that held the sub in position on rollers fixed to the cabin deck. He gave the craft a stiff shove and the big black tube, its top at shoulder height, moved towards the rear opening like some kind of organ of death. When the nose reached the edge of the cabin George gave it another push and it dipped down onto the ramp. Stratton kept tight to the bulkhead to avoid the large flotation pack fixed to the sub’s side. It tipped ungracefully off the end and dropped nose down towards the roiling water.

When it hit, Stratton stepped to the very edge of the ramp, the others following close behind. Everything that Stratton had told them about the next phase went through their minds. The seconds crammed together. The point of no return had arrived.

As the sub stabilised, the two inflation bags attached to either side of the body aiding its buoyancy, Stratton placed one fin on top of the other, leaned forward and dropped into the blackness. It seemed to take longer to fall than it should have. When he struck the water he disappeared beneath the surface. The others hesitated until he came back up.

Binning was first to follow, holding the plastic box tightly, closely followed by Jason. Rowena came next, with Jackson beside her. Smithy paused on the edge and looked as if he might refuse. Had George not given him a shove he might well have done. The skinny scientist let out a cry as he fell, arms and legs spinning like bicycle wheels, out of control.

Stratton pushed off hard with his fins to grab the side of the mini-sub. He had to release the flotation bags. Taking hold of the cable coupling, he yanked down on it. The bags drifted, the swell and the wind taking them into the darkness.The vessel dropped into a trough and Stratton pulled himself along it to the cockpit. The sub rose up the steep wall of the next wave, which broke over it, almost turning it over. Stratton was thrown into the cockpit. He struggled in the confined space to manoeuvre himself into the seat, hating how cramped the damned boats always felt when he was wearing operational equipment.

He couldn’t afford to search for the others yet. The water sloshed around his chin and he ripped off the fins, jamming them in the side of the seat. He turned on the instrument panel, plugged his breathing apparatus into the sub’s air outlet and put the mouthpiece in his mouth. He breathed in the oxygen, his mouth under the water more than not. The vessel leaned heavily and slid down into the next trough. If he didn’t bring the nose around into the waves it would tip over. Very inconvenient. He flipped the power switch and gave the propeller full throttle, twisting the rudder hard over.

The sub responded well, then seemed to stall. Stratton could feel the powerful electric motor working, yet the nose didn’t want to come around. The vessel slammed into the bottom of another deep seawater trench. As it came up the other side the nose suddenly turned as if it had been nudged by a greater power. The sub went almost vertically up the wall of water and gouged into the dark mass of the peak. It levelled out for a moment before tipping over to nose down into the next trough. He had it under a semblance of control.

Stratton looked out of the cockpit for any sign of the others. Two of them were hanging on to the passenger cabin and struggling to get inside. He twisted in his seat to look through the grille behind his head and saw movement. Something grabbed at his arm and a heavy limb struck him as Jackson scrambled unceremoniously in through the other side of the cockpit. The man’s size didn’t help. The tumbling rodeo-bull sub yawed at his arms as it lifted him and then dragged him under. No amount of training could have prepared him. Certainly not the bathlike waters of Puerto Rico where the US SEALs often did their initial mini-sub training. Jackson fell into the seat but then lost his fins after a wave smashed in through Stratton’s side of the cockpit and ripped them from his fingers. He almost drowned when a brute of a wave filled the cockpit before he’d found the end of his breathing tube. Stratton realised that the man was in trouble. He grabbed hold of Jackson’s mouthpiece, using the strap around his neck, found the end of the tube and plugged it into the panel outlet. Jackson put the mouthpiece between his teeth and coughed and spluttered as he fought to inhale. He’d nearly had it.

Stratton looked back outside the vessel to see that the bodies had gone. He hoped that meant they were all inside. He glanced up to see the rear of the Chinook, its ramp still open, a figure leaning out of the red glow. Stratton extended a thumb towards George, a gesture which looked to him as if it was returned. The huge chopper thudded away into the darkness and the sound of its rotors, a constant background noise for the past few hours, was replaced by the roar of the wind, the thrashing of the sea and the sizzle of the rain coming down in heavy sheets. Another streak of lightning lit up the sky and the rolling thunder that followed it seemed to surround them.

A hand came through the grille near Stratton’s face, its thumb in the air. It was Jason indicating that everyone was on board and connected to the sub’s air supply. Stratton blew the ballasts and the submarine began to sink.

The roller-coaster effect quickly reduced to nothing as the boat dropped beneath the water and away from the influence of the heavy swell. Stratton increased the throttle and the sub eased ahead under the power of its propellers.

Stratton plugged in a cable connected to his throat microphone and earplugs and looked over at Jackson who appeared to have gathered himself. He nudged the man and offered him a thumbs-up. Jackson returned the gesture, accompanied by a nod to confirm that he was okay. Stratton indicated his own mouth and mimicked talking with his fingers. Jackson searched for the ends of his throat-mike cables and plugged them into the sockets.

‘Can you hear me?’ Stratton asked, his voice sounding slightly strange.

‘That’s fine,’ Jackson said.

‘I can hear you both,’ another voice interrupted. It was Jason in the rear cabin.

‘Everything okay?’ Stratton asked.

‘Smithy’s lost a fin. We almost lost him. Otherwise all is well.’

‘Okay. Sit back and relax. The real ordeal is coming up.’ Stratton checked the positioning device, a sophisticated gyroscopic motion sensor that monitored and recorded the sub’s every move in every direction, constantly recalculating its position from memory. This negated the need for the sub to break the surface to get a GPS fix. He turned on the Doppler sonar, a sonic equivalent of radar, and a screen on the panel lit up, illuminating the faces of the sub’s occupants in a green-blue hue. The Doppler provided a three-dimensional image of the sub’s surroundings at various ranges. Stratton carried out a full scan as per operational procedure. As expected there was only one blip on the screen.

‘How far from the Morpheus?’ Jackson asked.

‘Just over three miles. We can’t get too close to the rig in these conditions or we’ll hit the anchor cables. We’ll drop out of the sub a klick uptide and float in. Jackson will reposition downtide. He’ll wait there until he gets your signal to break surface. He should be able to hold position until first light but you will be heading towards him long before that.’

‘Understood,’ Jason said.

Stratton pulled up the platform’s preprogrammed position and the navigation system gave the direction in the form of an arrow at two o’clock to their heading.

‘It’s all yours,’ Stratton told Jackson.

Jackson took over the controls. He struggled at first to maintain the correct depth but it was not long before he had the hang of it.

Stratton unplugged one of the cables. ‘What’s it like being back in the mob?’ he said.

Jackson glanced at him, suspecting that he was talking to him yet concerned at the same time. He looked down to see that the internal communications cable was unplugged and the conversation was purely between the two of them.

‘My guess is air force,’ said Stratton.

‘How did you know?’

‘A number of clues.’

‘I stayed in college until I got my master’s but I always wanted to be a fighter pilot. Couldn’t get it out of my system. So I joined up for a few years. It was pretty fantastic - everything I’d wanted as a kid. But I couldn’t help handing in design suggestions for weapons-guidance systems. One day I got a call from an office in London. The rest is history.’

‘I know the feeling,’ Stratton said.

‘This has the new periscope system, doesn’t it?’

‘Yes, but it’s no good in these waters. We don’t need it, anyway.’ Stratton checked the navigation system and the distance to the Morpheus. ‘This tide is moving.’ He plugged Jason’s voice cable back in. ‘You ready back there?’

‘We’re ready.’

‘In one minute Jackson’s going to stop the props. We’ll drift with the tide and be relatively stopped. We’ll have two minutes to clear the sub before Jackson will have to start the props again and get out of the track or hit the rig. I’m going to join you at the door. Hand me the grapnel launcher. You take the ladders and snag line. We’ll all go straight to the surface. You happy with that, Jason?’

‘Yes.’

‘Jackson?’

‘Yes.’

‘The signal to surface on completion of the task?’

‘Two thunder bombs.’

Stratton checked the navigation system again. ‘Okay. Put your tail to the platform and kill the speed.’

Jackson manoeuvred the vessel while Stratton pulled on his fins, disconnected the communications cable, removed his breathing apparatus and replaced it with the breather attached to the bottle strapped to his side. He eased out of the cockpit, a far less complicated exercise than climbing in, and moved along the casing to the cabin opening. The four scientists crammed inside the dark chamber looked at him. He indicated for them to exchange their breathing systems. They felt for the portable breathing teats.

Smithy had spent every second since leaving the helicopter in a state of abject fear. The jump had been bad enough but since the scramble into the sub all he’d been able to think about in the cramped dark cabin was Stratton’s comment about the climb up the platform.

When he received the signal to change from breathing off the submarine to his own air bottle he made one of the classic mistakes when it came to the procedure. He removed the sub’s breathing mouthpiece from his lips, let go of it and felt around for his own portable breathing set. When he did not find it immediately he tried to find the mini-sub mouthpiece again. He failed. Panic quickly set in.

He became hysterical in his efforts to find either mouthpiece. He didn’t think to find the bottle attached to his body and follow the tube from the end of it to the other end and the mouthpiece. He would soon have to take another breath, which would be all water, and he would die in that dark, cold and claustrophobic container.

When Stratton saw the stream of bubbles from the released mouthpiece and Smithy grabbing frantically at anything he knew immediately what was happening. The danger was not just to Smithy himself. His actions placed the lives of the others at risk. A drowning person had the strength of ten in their final acts of desperation and was more than capable of taking others with them. A grabbing hand would rip at anything - such as other people’s breathing tubes.

Stratton did the only thing he could. He reached inside the cabin, grabbed hold of the frenzied diver by his harness and, planting his feet against the outside casing, ripped the man out of the sub and released him into the ocean. Smithy continued to kick and panic, the water’s fluorescence lighting up around his beating limbs. He went into the blackness. Stratton had no idea whether he had gone up or down. But a second afterwards it no longer mattered. Not then, at least. It was done and they had their own lives to look after.

The incident had cost precious time that Jackson needed to avoid running into the rig. Stratton grabbed the grapnel launcher and beckoned the others to hurry. They were swift in their response and all three of them were soon out of the sub. As the propellers burst back into life the team headed towards the surface and the sub moved away into the gloom, the sound of its electric motor disappearing with it.

Stratton broke through to the surface first, the others a few seconds behind him. All of them stayed breathing from their air bottles, which would last another half-dozen minutes. The enormous rig stood several hundred yards away, lit up like the proverbial Christmas tree. A giant factory on legs, high above the storm waves. The sight of one of these towering structures never ceased to impress Stratton.

The others too looked in awe at the monstrous construction.They were unprepared for the sight of it so high above them in the water, in the dark. For a brief moment they forgot everything as they took in the suspended city. It looked almost alien to Jason, as if they were floating in a vast emptiness between planets and the platform was a twinkling space station.

Stratton suddenly thought of Smithy and as he rose up to the crest of the next wave he turned around in search of him. Rowena appeared to be doing the same. Neither of them could see the scientist and they forcibly removed him from their thoughts. There was too much to do to keep themselves alive.

Stratton removed his mouthpiece and slung the strap of the grapnel launcher over his head. He finned hard to keep his chin above the water. ‘Where’s the snag line?’ he shouted.

Jason removed his mouthpiece and held up the thin, neatly coiled nylon cord that had a collection of karabiners attached to it.

Stratton took the line and hooked one of the karabiners to Jason’s harness. He held another, connected by a metre-long line to Jason’s, and looked for Binning who was drifting away from the group, staring up at the oil platform as if mesmerised by it.

‘Binning!’ Stratton shouted.

The man came out of his reverie, took out his mouthpiece and finned hard to rejoin them.

Stratton attached the karabiner to his harness. ‘You two swim that way. Stretch the line tight between us. Move it.’

Jason detected anxiousness in the operative’s voice but a glance at the rig revealed why. They were closing on it with surprising speed. It was getting bigger by the second. The four of them dropped down the side of a steep trough as if sliding down the side of a hill.

Jason and Binning began to fin as hard as they could away from the others.

Stratton unceremoniously grabbed Rowena, snapped the remaining karabiners to her harness and his own and swam away on his back, yanking her along. Her head went under for a moment and she surfaced coughing and spluttering. She fought to control her reaction to the swallowed water and finned hard to keep up with Stratton. The thought of being a liability to the SBS man horrified her almost as much as the possibility of drowning did.

The pairs quickly moved apart as they closed on the Morpheus’s four huge black-steel piles.

Stratton singled out the leg he wanted to snag, gauging their approach. That was the tricky part, or the latest in a series of them. As the powerful tide pulled them towards the leg it became obvious to them all that if they got it wrong and missed, or even bounced off and were unable to get a pair either side, then they would sail on into the black ocean beyond. They would fail.

The current took the team in a wide curve rather than a straight line. Stratton calculated that they were too far to one side. ‘Fin!’ he shouted and Rowena responded. They lay on their backs and climbed the side of another huge swell and finned as hard as they could. The line went tight as the pair went over the peak. Stratton followed it to where it disappeared into the next wall of water. He hoped that Jason and Binning had made the same calculation. Suddenly the line went slack, indicating that they had. ‘More!’ shouted Stratton and they gave it another hard effort. They stopped to reassess their track and Rowena spat out salt water, her face cold but her body warm inside the rubber suit.

They were back on target and as they reached the peak of a swell Stratton took a second to study the levels of the platform still a couple of hundred metres away. He could see a haze of lights and not much else. If there were people outside, he couldn’t see them. Yet he had the same advantage. Even an alert enemy couldn’t see him. For now.

He had another advantage: the hijackers had no idea when they were coming. The enemy could watch the water constantly for any sign of a swimmer but it would be difficult to spot one. With such a large area to observe, at night in particular, it would be almost impossible to find a black-suited target in the rolling water. Night-vision goggles would reveal little unless they were trained directly on the swimmer. The same went for a thermal imager - the team’s cold faces gave off hardly any heat and the rubber dry-suits masked their body warmth. A watcher on the exposed lower levels would struggle to make them out in these conditions.

But they needed to be lucky. If the watcher was there and did somehow see them he could pick them off with relative ease from one of the lower spider decks if he had a rifle.

The legs of the Morpheus loomed closer. They’d gone off track again: another adjustment was required, this time in the other direction. Together they swam towards Jason and Binning who were out of sight beyond the next peak. The line went taut again, indicating that the two men had made the same assessment.

The massive legs became dark pillars astride a vast blacked-out cave, the structure no longer distant enough to be encompassed in a single gaze. The ceiling lights in the lower decks shone so brightly down onto the water that it seemed impossible to the divers that they could not be easily seen. Stratton had thought the same the first time he’d made such an approach. But after reversing position to watch another team close in on a well-lit area he knew how difficult it was to see a blackened body unless the watcher knew precisely where to look.

They rose and fell on the rolling sea, a good fifty metres apart and rarely visible to each other, the line connecting them seesawing as one hit a peak and the other a trough.

It grew suddenly darker as they moved into the shadow of the platform and past the perimeter of lights, heading directly beneath the overhanging balconies of the decks, the leg expanding visibly as they got closer. Rowena and Stratton passed close to another leg that was coated all the way round with a thick layer of barnacles clustered at the waterline. The waves struck the vast supports and the booming noises that they made rebounded around the platform cave.

The leg diameter was the length of a bus. Stratton’s gaze darted between it and the line. Jason and Binning became visible briefly on the top of a swell and Stratton knew they would hit it perfectly.

The troughs exposed the gnarled barnacles that Stratton knew from experience were razor sharp. ‘Watch out for the barnacles!’ he shouted to Rowena. It was just another problem to add to the load she already had.

They rose up onto a peak as they came alongside the curved wall of steel. The wave slammed into the upright, the frothy water reaching up towards the first cross-beams. Stratton was drawn into the leg and stuck out his feet to fend it off. Solid. And sharp. The barnacles scratched his fins as he went by.

Jason and Binning went down the other side and the line wrapped around the leg. The pairs moved closer together as they slid down into another trough. The line suddenly went taut and yanked them to a brutal halt.

It was like being dragged along by a boat now. The sudden change pulled them lower in the water and it was much harder to keep breathing air. When they were at the peak of the wave they were almost dragged under and when at the trough the force was trying to yank them higher. They’d hit the leg in the middle of the line so they were held almost the same distance - its width - from it. They could hardly see anything directly beneath the platform, only a few rays of light finding their way between the girders.

Stratton lay on his back, holding on to the line. He searched the nearest girders for signs of life. The wind and rain whipped through the structure in gusts and squalls, beating tirelessly against the metal. If there was someone hiding in the darkness above they would be invisible but they would also have to be holding on tight or lashed to a span. And if they were, they could not stay there for long. Stratton felt confident that the team was not being observed.

He pulled the grapnel launcher from around his neck, took hold of the stock and trigger grip and selected the ideal spar. The air-powered device had been primed since before they’d left the Chinook and Stratton removed the bungee that held the grapnel in place, checked that the line was free to uncoil and then removed the safety catch. He put the butt against his shoulder and raised the grapnel end skyward. The heavy sea made it difficult to maintain position long enough to get off an accurate shot.

‘Hold me!’ he shouted.

Rowena pulled herself to him and grabbed him from behind, her hands gripping his harness, her legs finning as hard as she could. Her head went under the water and she spluttered when she surfaced but maintained her grip. She would not be able to do it for long since the difficult position kept her head under the water more than above it. Well aware of her situation, Stratton quickly aimed once again. The angle was crucial. Too high and the wind might blow it back once it had reached its full length of cable. Too low and he risked hitting the span itself or having the grapnel fly beneath it.

He felt Rowena go under but waited until they rose to the top of a wave, reducing the distance to the span by a third. As she surfaced he fired.The butt of the launcher punched into his shoulder and they both went under the water. When they surfaced at the bottom of a trough, Rowena almost choking, they could see the all-important double cable lying over the span, the ends still attached to the launcher. The grapnel had got over the spar.

Stratton let go of the gun, kept hold of the lines and pulled on them as quickly as he could. The lightweight tungsten grapnel came out of the water up towards the span and one of the claws snagged hold of a corner. He gave it a firm jerk to ensure that it was secure. ‘Hand me your caving ladder,’ he said.

Rowena unhooked the rolled alloy ladder from her harness and handed it to him. Stratton attached the karabiner on the end of the ladder to the end of one of the lines and pulled down on the other. The line passed through a one-way device on the grapnel and the ladder rose out of the water towards the span.

Jason and Binning watched somewhat helplessly as they rose and fell on the swell. A huge wave slammed against the leg sending water cascading over them, the boom that it made sounding like thunder. It jolted the line powerfully and as Jason traced the cable back to the leg the dropping swell exposed it. To his horror he saw that it was fraying. ‘Stratton!’ he called. ‘The line!’

Stratton recognised the danger. He’d seen it before, a bad combination of extremely heavy seas and barnacles. They had to hurry. He released the line and it sank immediately with the weight of the launcher on the end of it. The lone caving ladder hanging from the spar was now their only way out of the water. Its end dangled in the water several metres away. It was across the tide, a high-risk quick burst away to bridge the gap. If he missed it he would float out to sea.

Stratton unhooked the karabiner that held him to the snag line, waited for the next trough and finned hard towards the ladder. As he came off the line Rowena got dragged closer to the leg by the greater weight of Jason and Binning.

Stratton caught hold of the ladder. ‘Binning,’ he called out immediately as he ripped his fins off and let them go. ‘You. Now. To the ladder. Let’s go.’

Binning did not hesitate. He unhooked himself and made a supreme effort to reach Stratton, which he did more easily than he had expected to. Stratton grabbed him at the same time with a free hand.

‘I’ve got it,’ Binning spluttered.

‘If you can’t carry your gear, hook it to the bottom rung of the ladder. We’ll haul it up later.’

Binning shook his head. ‘I’ll be fine.’

The climb. Not a simple affair in calm conditions. In a storm a bad dream. Requiring a combination of iron strength and real skill. In a heavy swell the trick was knowing when to begin.

‘Dump your fins,’ Stratton said. ‘Wait until we’re at the peak, then climb as fast as you can.’

‘The line’s going to break,’ Jason called out.

‘Move your arse!’ Stratton urged Binning.

As they rose up the next swell Binning unstrapped his fins, frantically wiggling them free, and at the same time struggled to grip the ladder. They went up as if they were on an escalator.

‘Grab high as you can! Now!’ Stratton shouted.

The wave peaked and Binning reached for the highest rung he could. When the water dropped he dangled like a fish on a hook, his hands bearing the weight of his body, suit and equipment. He fought to get a foot on a lower rung to take some of the strain from his fingers.

Some forty feet below him now, Stratton watched Binning cycling in the air. ‘Climb, Binning! Climb!’

If Binning did not gain a few feet before the top of the next wave arrived it would punch him off. He climbed for all he was worth. The peak struck his legs hard but he hung on.

‘Go!’ Stratton urged.

Binning focused his strength and as he closed on the span Stratton turned his attention to the others. ‘Disconnect together as I start my climb!’ he called out.

‘You ready?’ Jason shouted to Rowena.

‘Yes!’ she shouted.

The fraying line, however, was a second ahead of them and as Jason unclipped his karabiner the line snapped and both of them shot away from the leg.

Stratton was about to start his climb when he saw that Rowena wasn’t going to make it to the ladder. He slid down as the trough dropped away, grabbed hold of a lower rung and lunged in the direction of her track. Jason made the ladder and grabbed a firm hold on it that did not help matters. Rowena finned towards Stratton as hard as she could but as they stretched out their arms towards each other their fingers barely touched. She passed him by, staring at him, finning madly even though they knew it was hopeless.

The line attached to Rowena suddenly went taut. She was yanked to a stop as Stratton lurched towards her, twisting the line that he had managed to grab with his free arm while holding on to the ladder with the other. Jason made a grab for the line and together they began to win the battle of hauling her in.

‘Swim!’ Stratton shouted as a heavy swell suddenly put her above them.

Binning reached the top of the ladder and hauled himself over the span in time to see the drama below.

Rowena grabbed Stratton’s arm and pulled herself along it to his harness where Jason helped to hold her.

‘Climb!’ Stratton ordered him. ‘It won’t hold three of us for long!’

Jason ripped off his fins and as they went up the wall of water he grabbed the highest rung that he could reach. The swell moved on and when his foot found a rung too he climbed as quickly as he could.

‘Go!’ Stratton said urgently to Rowena before Jason had reached the top.

She gritted her teeth, then took a deep breath before ducking below the water to remove her fins. Stratton kept hold of her as they rose up the next wave and at its peak she surfaced, grabbed a rung of the twisting ladder and began to climb. She was strong and nimble, which Stratton was thankful for. He hung on for dear life as the water fell away beneath him. With the next swell, he followed behind her to the top.

Binning and Jason helped them onto the wide spar and when they were all secure the four of them remained seated for a moment to thank whatever gods might have helped to get them through the last hour.

Rowena looked across at Stratton, her breathing laboured. ‘Thanks,’ she said. It seemed difficult for her to say it.

He ignored her. There was no need for gratitude. It was what team members did for each other.

‘This might be an appropriate time to spare a thought for Smithy,’ Jason said.

‘I suggest you stay focused on your own lives,’ Stratton advised. ‘You may yet join your colleague.’

The platform shuddered as the waves crashed relentlessly against the legs. Stratton eyed the upper structure that was a web of crisscrossing steel spars. Light filtered through grilles in the decking, creating shadows and dark spaces.

‘Where do you need to place your device?’ Stratton asked.

‘The higher the better,’ Binning replied. ‘Especially in this weather.’ He got to his feet and scanned the complex of black steel above as if looking for the ideal spot. ‘I see why they call them spider decks.’

‘How do we get up there?’ Jason asked.

Stratton indicated the nearest leg. ‘From here on we’ll have to use the rungs. Not the best option but we don’t have the kit for anything else. I’ll lead. Beware of booby traps. Keep an eye out for taut wire or fishing nylon. If in doubt, don’t touch it. Let me know.’

Stratton got to his feet and removed the bungee that secured the silenced SMG to his waist. He gave it a brief check and left it to hang from the strap across his back. He felt for the pistol in its holster at his thigh. Satisfied, he made his way across the spar to one of the vast legs and the rungs that led up into the gloom.

‘Whenever you’re ready,’ he said, looking back at them.

Binning was right behind him.