It was a ten-pfennig ride on the U-Bahn to the Zoo Station, repainted to look especially smart for the Olympic fortnight. Even the walls of the houses backing on to the station had been given a new coat of white. But high above the city, and where the Hindenburg airship droned noisily back and forwards towing an Olympic flag, the sky had gathered a surly gang of dark-grey clouds. As we left the station, Inge looked upwards and said: ‘It would serve them right if it rained. Better still, if it rained for the entire fortnight.’

‘That’s the one thing they can’t control,’ I said. We approached the top of Kurfürstenstrasse. ‘Now then, while Herr Haupthandler is away with his employer, I propose to have a squint at his rooms. Wait for me at Aschinger’s restaurant.’ Inge began to protest, but I continued speaking: ‘Burglary is a serious crime, and I don’t want you around if the going gets tough. Understand?’

She frowned, and then nodded. ‘Brute,’ she muttered, as I walked away.

Number 120 was a five-storey block of expensive-looking flats, of the sort that had a heavy black door that was polished so keenly they could have used it as a mirror in a negro jazz-band’s dressing room. I summoned the diminutive caretaker with the enormous stirrup-shaped brass door-knocker. He looked about as alert as a doped tree sloth. I flashed the Gestapo warrant disc in front of his rheumy little eyes. At the same time I snapped ‘Gestapo’ at him and, pushing him roughly aside, I stepped quickly into the hall. The caretaker oozed fear through every one of his pasty pores.

‘Which is Herr Haupthandler’s apartment?’

Realizing that he was not about to be arrested and sent to a KZ, the caretaker relaxed slightly. ‘The second floor, apartment five. But he’s not at home right now.’

I snapped my fingers at him. ‘Your pass-key, give it to me.’ With eager, unhesitating hands, he produced a small bunch of keys and removed one from the ring. I snatched it from his trembling fingers.

‘If Herr Haupthandler returns, ring once on the telephone, and then replace the receiver. Is that clear?’

‘Yes, sir,’ he said, with an audible gulp.