My plane was leaving on the Monday night and I asked Peter if he could take me to one of the galleries – I didn’t know much about art, but I felt I wanted a big painting. He took me to one of the downtown galleries which was selling an Andy Warhol painting. It was of Mick Jagger from three sides – very particular, and very tall. I thought it was great, and I paid $50,000 for it. I brought it back to Europe, but where in Europe? My girlfriend at the time was Karen Schultz, who lived in Hamburg. I was living in Monte Carlo but because of all my travel to tournaments I was seldom there, and I felt it ought to be seen, so I sent the shipment to Karen’s apartment in Hamburg where it hung, and I saw it when I went to stay with her. After two or three years unfortunately our relationship ended, and she asked me what I wanted her to do with the painting. I said ‘You know what, leave everything. I don’t know what to do with it, you seem to like it, I don’t know where to put it in Monte Carlo, I’m on the road the whole time anyway. You have it, it’s yours.’ That was 1991.

After that we kept in touch, we saw each other once a year, Karen wrote me beautiful letters on my birthday and Christmas, and we kept in contact long-distance. She was a really classy girl – my mother and sister both liked her. After studying, she became a school teacher, moved to Dresden, got married, and had a baby daughter. Then in 2009 she contacted me, said unfortunately her marriage hadn’t lasted, and that she had to downsize, and the Warhol painting was just too big for her new flat – so could she give it back to me? Karen is a very intelligent and beautiful woman, not financially well off, but she had integrity. I told her she could keep it, but she said no, it didn’t feel right for her to have it. The painting was by then worth between €2–3 million! She was struggling financially after the break-up of her marriage, but she said it didn’t feel right for her to sell it.

Karen said she would send it to me, but once it was clear that she really didn’t want it, I asked my friend and physiotherapist Waldemar Kliesing to drive to her apartment, pick it up, and take it to a safe place. I didn’t know where to put it, and at first it went to Leimen where it spent six months in my mother’s cellar – I was worried that my mother would spill something on it. Then after six months I decided it wasn’t safe and I sent it to a good friend in Munich who’s an art expert, and he currently has it until I work out what to do with it. I tell the story to show what a classy person Karen is. It was hers. I kept asking her what I could do for her if she didn’t want the painting, but she wouldn’t accept anything. She’s a different animal, an unbelievable person – they don’t make people like her any more.

My good form from the end of 1988 continued into 1989. I won the titles in Milan and Philadelphia, was runner-up in Monte Carlo and had a very good clay season, which meant I went to the French Open full of confidence. I survived a five-setter against Guillermo Perez-Roldan in the fourth round, but those were the only sets I dropped before playing Stefan Edberg in the semis. I knew that waiting in the final was not one of the big names of clay court tennis like Lendl, Wilander or Noah, but a 17-year-old called Michael Chang. It was a golden opportunity for me. I came back from two sets down and was a break up in the fifth, but I lost. I had sleepless nights after that. I can’t say I’d have beaten Chang in the final, but I would certainly have been favourite. I felt I’d blown the French.

It made me very motivated for the next Slam, which was Wimbledon, but it also made me feel I had to do something a bit different. So I skipped Queen’s and played the tournament in Hoylake, near Liverpool. I won that tournament on the Saturday and played my first match at Wimbledon on the Monday. But it all went well and I felt really strong. I won five matches in straight sets to set up a semi-final against Ivan Lendl.

The one thing that’s underestimated by people who haven’t played at the highest level is that, because a Grand Slam is two weeks, there’s a totally different dynamic about it. You cannot stay on the same emotional level for two weeks, it’s impossible, and so you go through ups and downs. Think of any two-week period: how many ups and downs do you go through? That happens to us during a tournament, we are always vulnerable to a low at some stage – therefore some matches we’re just pleased to get through, even if the score doesn’t look great. I had a low on the day of that semi-final, and because of the French Open loss – also a semi-final – the demons came back, and Lendl took advantage. He was having his best grass court season, he’d won his first title at Queen’s with most of the top grass courters in the draw, and he was on a winning streak. I won the first set, but he played a good tiebreaker in the second, and I was so angry about the way I had played the breaker that he broke my serve twice at the start of the third. He had me.

But thankfully the rain came. In those days we didn’t have the roof, so with him leading 3-0 on two breaks of serve in the third set, I was pleased to get off court and take a shower. That allowed me to regroup, and then I beat him pretty fair in the fifth set.

That was the break I needed. The semi-final had taken place on Saturday because of rain on the Friday, so I didn’t have too much time to think about the final against Edberg. But I was determined not to be careless after the heartache of 1988. I was out for redemption. I was so ready to play because of the pain I’d felt in the previous year that I took the first set 6-0. He got into it in the second, but I beat him in straight sets. It was a great day for West Germany – because of more rain on Saturday, the women’s final was played on the Sunday too, and Steffi Graf beat Martina Navratilova, meaning we had two West German winners that day.