‘By this time of course Grete was married to Paul, and was devoted to him. For his part, Paul was never worthy of her. I suspect he was rather more keen on my family name and money than he was on my daughter. But to everyone else they must have seemed like a perfectly happy couple.

‘Well, all that changed overnight when Grete finally tracked down her real mother. The woman was a gypsy from Vienna, working in a Bierkeller on Potsdamer Platz. If it was a shock to Grete it was the end of the world to that little shit Paul. Something called racial impurity, whatever that amounts to, gypsies running the Jews a close second for unpopularity. Paul blamed me for not having informed Grete earlier. But when I first saw her I didn’t see a gypsy child, but a beautiful healthy baby, and a young mother who was as keen as Lisa and I that we should adopt her and give her the best in life. Not that it would have mattered if she’d been a rabbi’s daughter. We’d still have taken her. Well, you remember what it was like then, Herr Gunther. People didn’t make distinctions like they do these days. We were all just Germans. Of course, Paul didn’t see it that way. All he could think of was the threat Grete now posed to his career in the S S and the Party.’ He laughed bitterly.

We came to Grünau, home of the Berlin Regatta Club. On a large lake on the other side of some trees, a 2,000-metre Olympic rowing course had been marked out. Above the noise of the slipper’s engine could be heard the sound of a brass band, and a public-address system describing the afternoon’s events.

‘There was no reasoning with him. Naturally, I lost my temper with him, and called him and his beloved Fuhrer all sorts of names. After that we were enemies. There was nothing I could do for Grete. I watched his hate breaking her heart. I urged her to leave him, but she wouldn’t. She refused to believe that he wouldn’t learn to love her again. And so she stayed with him.’

‘But meanwhile he set out to destroy you, his own father-in-law.’

‘That’s right,’ said Six. ‘While all the time he sat there in the comfortable home that my money had provided for them. If Grete did kill him as you say, then he certainly had it coming. If she hadn’t done it I might have been tempted to have arranged it myself.’

‘How was he going to finish you?’ I asked. ‘What evidence was there that was so compromising to you?’

The slipper reached the junction of Langer See and Seddin-see. Six throttled back and steered the boat south in the direction of the hilly peninsula that was Schmöckwitz.