The Unter den Linden gaped ahead of them. It had lost its lime trees in “36 — cut down in an act of official vandalism at the time of the Berlin Olympics. In their place, on either side of the boulevard, the city’s Gauleiter, Josef Goebbels, had erected an avenue of ten-metre-high stone columns, on each of which perched a Party eagle, wings outstretched. Water dripped from their beaks and wingtips. It was like driving through a Red Indian burial ground.

March slowed for the lights at the Friedrich Strasse untersection and turned right. Two minutes later they were parking in a space opposite the Kripo building in Werderscher Markt.

It was an ugly place — a heavy, soot-streaked, Wilhelmine monstrosity, six storeys high, on the south side of the Markt. March had been coming here, nearly seven days of the week, for ten years. As his ex-wife had frequently complained, it had become more familiar to him than home. Inside, beyond the SS sentries and the creaky revolving door, a board announced the current state of terrorist alert. There were four codes, in ascending order of seriousness: green, blue, black and red. Today, as always, the alert was red.

A pair of guards in a glass booth scrutinised them as they entered the foyer. March showed his identity card and signed in Jost.

The Markt was busier than usual. The workload always tripled in the week before the Fuhrertag. Secretaries with boxes of files clattered on high heels across the marble floor. The air smelled thickly of wet overcoats and floor polish. Groups of officers in Orpo-green and Kripo-black stood whispering of crime. Above their heads, from opposite ends of the lobby, garlanded busts of the Fuhrer and the Head of the Reich Main Security Office, Reinhard Heydrich, stared at one another with blank eyes.

March pulled back the metal grille of the elevator and ushered Jost inside.

The security forces which Heydrich controlled were divided into three. At the bottom of the pecking order were the Orpo, the ordinary cops. They picked up the drunks, cruised the Autobahnen, issued the speeding tickets, made the arrests, fought the fires, patrolled the railways and the airports, answered the emergency calls, fished the bodies out of the lakes.