At the top were the Sipo, the Security Police. The Sipo embraced both the Gestapo and the Party’s own security force, the SD. Their headquarters were in a grim complex around Prinz-Albrecht Strasse, a kilometre south-west of the Markt. They dealt with terrorism, subversion, counterespionage and “crimes against the state”. They had their ears in every factory and school, hospital and mess; in every town, in every village, in every street. A body in a lake would concern the Sipo only if it belonged to a terrorist or a traitor.

And somewhere between the other two, and blurring into both, came the Kripo — Department V of the Reich Main Security Office. They investigated straightforward crime, from burglary, through bank robbery, violent assault, rape and mixed marriage, all the way up to murder. Bodies in lakes — who they were and how they got there -they were Kripo business.

The elevator stopped at the second floor. The corridor was lit like an aquarium. Weak neon bounced off green linoleum and green-washed walls. There was the same smell of polish as in the lobby, but here it was spiced with lavatory disinfectant and stale cigarette smoke. Twenty doors of frosted glass lined the passage, some half open. These were the investigators” offices. From one came the sound of a solitary finger picking at a typewriter; in another, a telephone rang unanswered.

“ ‘The nerve centre in the ceaseless war against the criminal enemies of National Socialism’,” said March, quoting a recent headline in the Party newspaper, the Volkischer Beobachter. He paused, and when Jost continued to look blank he explained: “A joke.”