One of those had been Franz Rauter, a bright and well-regarded Abwehr career officer who was running a successful spy ring in England and was therefore protected from the purges towards the end of the war. The rumour was that he was now helping the British.

Now Klaus Böhme observed a man who looked very much like Franz Rauter chatting amicably with a man and a woman in civilian clothes, neither of whom appeared to be Russians. After a friendly farewell, he was put into handcuffs and led towards his block.

As he queued for supper later that afternoon, Böhme spotted the same man ahead of him on the landing. He heard a guard address him as Möller, but when the man turned his head, Böhme had absolutely no doubt. If Rauter was here – under an assumed name – it was because he was a traitor. Böhme knew what his duty was, and it wasn’t as if he had anything to lose. They might even put him out of his misery sooner.

He collected his supper and walked towards the man, whose back was towards him. ‘Hey, Franz – Franz Rauter!’

Instinctively Rauter turned. In the brief moment before Böhme plunged the knife deep into his heart, he recognised the young man who’d called his name but couldn’t for the life of him place him.

His memory was so bad these days.

Alphonse Schweitzer was unaware of all this. He was still in Block D. The governor had come to his cell that afternoon and informed him Marshal Zhukov had reviewed his case and denied his petition.

‘What does that mean?’

‘What do you mean, what does that mean? It’s obvious, isn’t it? You’re going to be executed after all – at dawn tomorrow. You’ll be transferred to the death block now.’

Schweitzer was dragged crying from his cell at dawn the next morning. The guards were disgusted at having to handle the terrified prisoner, who’d soiled himself and kept vomiting. He was thrown in the back of a truck and driven the short distance to the barracks, then dragged to the firing range.

A white-faced Catholic priest was allowed to spend a few seconds with him, but Schweitzer couldn’t hear what he was saying and nor did he care.

As he was strapped to a post, he felt his legs give way. At that moment a tall man in a commissar’s uniform strolled over to him. The man – who looked suspiciously like a Jew – smiled as he instructed the guards to gag the prisoner but not to bother blindfolding him. ‘Let him enjoy everything!’

Once he was trussed up like a pig, the commissar leaned over and spoke clearly in his ear. ‘I really must thank you, Schweitzer: you’ve no idea how helpful you’ve been!’

When Hanne and Prince met with Commissar Gurevich in his office in Behrenstrasse later that morning, the mood could not have been more sombre. Prince had listened to the Russian’s account of Schweitzer’s execution without showing any reaction, and simply shrugged when informed that the prisoner had been told how helpful he’d been just before he was shot.