Dryden left Humph parked up on the bank with his Greek language tape, six diet chicken and mayonnaise sandwiches, and a miniature bottle of Metaxa 3-star brandy. He got himself a pint of bitter in the pub and cradled a well-wrapped bottle of decent whisky under one arm. He needed more information about Johnnie Roe’s secret life, and the Water Gypsies traded in best single malt.

Did Lyndon or Estelle know Johnnie was Maggie Beck’s lover? Did they know that they’d met at the pillbox as lovers?

He set off south along the river bank past the ghostly white forms of the floating gin palaces which made up 80 per cent of the summer traffic on the main river. Each one was a hymn in fibreglass to the enduring bad taste of the English middle classes. Brass bristled at every vantage point while miniature ensigns and Union Jacks hung from useless masts.

Life, such as it was, within these floating suburban semis was oddly public. In one, a large middle-aged woman was lying on a bunk bed eating chocolates in her bra and knickers, presumably under the impression that while she could see passers-by on the towpath they couldn’t see her. In the next a couple traded insults over a folding dinner table stacked high with a takeaway curry and a two-litre bottle of Chianti. In a third a large Dobermann pinscher scrabbled its paws along the porthole windows as Dryden hurried past with his pint.

Soon he left the up-market tastelessness of the summer tourist trade behind. The bright lights of the Cutter disappeared round a bend in the river and the moorings were taken up with narrow boats. Some were in darkness and even in the late evening of a long summer’s day the accumulated damp of a dozen spendthrift winters was in the air. Most bore the scars of homemade patches and makeshift repairs. A few sported wind generators, and even cheap solar panels.

Dryden took a gulp from his pint, pausing by the Solar Wind, a narrow boat painted jet black but studded with hand-painted stars. The windows showed no light but from somewhere the distinct aroma of hash drifted with the mist off the river. Dryden treated himself to half a dozen lungfuls and pressed on. He found the Middle Earth at the end of the line. It had four rectangular windows at towpath level and light flooded out of all of them. This far out along the towpath passing walkers rarely strayed. There were no lights on shore and the reputation of the boat’s crews guaranteed a certain exclusivity.

Dryden approached the first lighted window and watched without surprise a male bottom rising rhythmically, accompanied by faint whimpers of pleasure. Dryden expected similar scenes might be viewed in the other windows, but he checked each to make sure.

‘Excellent,’ he said, finishing the pint of beer. ‘An orgy.’

He put a foot on the narrow boat’s back landing stage and thumped hard on the roof of the Middle Earth, settling his now empty pint into one of the flower pots.

A motheaten man with no clothes and a wayward erection threw open the rear double doors.

‘Nice out,’ said Dryden, grinning.

‘Dryden. What the fuck do you want?’

Dryden looked suitably affronted. He held up the bottle of malt whisky. ‘I’ve got this for Etty – and a tenner for information received.’

Etty appeared, having recently extracted herself from under the pink bottom. Dryden felt a brief but intense surge of jealousy.

‘Dryden. Welcome. Why the clothes?’

‘Call me conventional. Can I…?’

Garments were being hastily draped over various genitalia and all the blinds on the Middle Earth were belatedly drawn. Dryden counted five girls and three men and tried not to work out what had been going on. Someone produced glasses and he poured out the malt.

There was a satisfying fug in the closed compartment enhanced by the aroma of a recently devoured vegetable curry. Tin dishes with livid green stains obscured the map table. The light came from a single storm lamp with a gas wick. A calendar hanging by the sink listed organic recipes while on the draining-board a pile of freshly picked carrots waited to be washed. Dryden guessed these had been liberated from a nearby field.

Etty sniffed the tenner Dryden had given her and secreted it amongst the underclothes which surrounded her. ‘I was actually looking for some more information,’ said Dryden, sipping his own malt.

The bloke with the erection and one of the girls shuffled off towards the forward cabin, presumably to conclude unfinished business.

But Etty had sharpened up, overcoming the effects of whatever she’d been smoking. ‘About…’

‘Johnnie Roe. The people smugglers. They used to use the Ritz, but now that’s closed down. And they had people living up at the old air base at Witchford. The police are on to that too. So – unless they’ve stopped the lorries, which I doubt, they must be operating out of somewhere else. Any idea where?’

‘Why would we know…?’ It was Etty’s partner. He was thin, with sandy hair, and a pointy beard like Catweazel. He began to roll a plump spliff. When he lit it he took about a centimetre off the beard, and there was a faint smell of old-fashioned barbers in the air.

Dryden ignored him and looked at Etty. ‘There’s some new pickers out for the harvest,’ she said. ‘They arrived the day before yesterday. My guess is their papers are phoney. They get dropped off by van for the night shifts. They don’t know exactly where they’re living and their English isn’t great, but I heard them talking. There’s a lot of languages, but English is the only one they share. They call it the silos – where they’re sleeping. They’re pretty unhappy with it as far as I can gather – no shops around, no nothing.’

‘Silos?’ said Dryden.

Etty finished her malt and licked her lips. ‘A cluster of them. It has to be Sedge Fen. The old grain works.’