‘And you say he was released?’

‘Unfortunately, but a sergeant checked his name out and found him on our watch list. Fortunately the system appears to have worked sufficiently well for us to find out about it, what… three days later?’

‘We need to get someone out to Munich, Christopher.’

‘I’d like to volunteer, sir.’

‘I need you here.’

‘Why, sir? The war’s over and we’re not running agents any longer. I speak German and I know the case – and I’ve worked in Europe on clandestine missions: this one ought to be much more straightforward.’

Later, Major Lean reflected that Stephens had sounded a bit too complacent, too careless of the danger that still existed in Germany despite the Allied victory. But by then it was too late.

Captain Stephens arrived in Munich two days later. The American military police were somewhat chastened by their failure to detain a man identified to them as a Gestapo officer, and did what they could to help.

The young sergeant from Chicago who’d found the Ferret’s details on the watch list was assigned to help the captain. He took him to the bar north of the station where the fight had taken place, and eventually they traced one of Emil’s friends. Emil himself had left town, but the friend told the British officer what he knew: that the man who said he was known as das Frettchen was from Vienna, that he carried a Gestapo identity badge and had stolen a young prostitute from Emil, a girl called Gisela.

It was only when he was threatened with arrest that he revealed more. It’s only rumours, but Emil told me he’d heard this Austrian was living with Gisela near the Theresienwiese.

For the next few days Christopher Stephens hung around the bars of central Munich, and especially those near the Theresienwiese, asking people if they knew a young Austrian – maybe from Vienna – known as das Frettchen. He was generous with whoever talked to him, buying drinks and promising rewards if they could help him find the man.

But he wasn’t careful enough. He forgot that this was Munich, the city where the Nazi Party had started and that could still be regarded as its heartland. One man who overheard Stephens in a bar became suspicious and didn’t believe the story about the young Austrian owing him money. He mentioned it to a friend, who told someone else, a man who’d been an SS officer and was now living under an assumed identity. This man contacted someone he knew who’d been in the Paris Gestapo, and fairly soon word reached a man in Frankfurt who said not to worry, he’d take care of matters.

Ulrich and Wolfgang Steiner had first met in late 1943, and instinctively trusted each other. It was immediately apparent to Steiner that they could not be more different: one a working-class Protestant from Lower Saxony, the other a middle-class Catholic from Vienna. Ulrich had joined the SS as a private and worked his way up through the ranks, gaining a reputation for being especially ruthless. He’d lost an arm at the Battle of Kursk, and after that was based in Berlin, where the two men had got to know each other. Sometime in late 1944 Steiner provided Ulrich with an excellent new identity, and in return, Ulrich – who was very well connected in the SS – promised to act as a point of contact for both Wolfgang and his son.