They finished their meal. The restaurant began to empty out. As their coffee was served, they were joined by the owner, Walter’s distant cousin Robert von Ulrich, and the chef, Jörg. Robert had been a diplomat at the Austrian Embassy in London before the Great War, while Walter was doing the same thing at the German Embassy there – and falling in love with Maud.

Robert resembled Walter, but was more fussily dressed, with a gold pin in his tie, seals on his watch chain, and heavily slicked hair. Jörg was younger, a blond man with delicate features and a cheerful smile. The two had been prisoners of war together in Russia. Now they lived in an apartment over the restaurant.

They reminisced about the wedding of Walter and Maud, held in great secrecy on the eve of the war. There had been no guests, but Robert and Ethel had been best man and bridesmaid. Ethel said: ‘We had champagne at the hotel, then I tactfully said that Robert and I would leave, and Walter –’ she suppressed a fit of giggles – ‘Walter said: “Oh, I assumed we would all have dinner together”!’

Maud chuckled. ‘You can imagine how pleased I was about that!’

Lloyd looked into his coffee, feeling embarrassed. He was eighteen and a virgin, and honeymoon jokes made him uncomfortable.

More sombrely, Ethel asked Maud: ‘Do you ever hear from Fitz these days?’

Lloyd knew that the secret wedding had caused a terrible rift between Maud and her brother, Earl Fitzherbert. Fitz had disowned her because she had not gone to him, as head of the family, and asked his permission to marry.

Maud shook her head sadly. ‘I wrote to him that time we went to London, but he refused even to see me. I hurt his pride by marrying Walter without telling him. My brother is an unforgiving man, I’m afraid.’

Ethel paid the bill. Everything in Germany was cheap if you had foreign currency. They were about to get up and leave when a stranger came to the table and, uninvited, pulled up a chair. He was a heavy man with a small moustache in the middle of a round face.

He wore a Brownshirt uniform.

Robert said coldly: ‘What may I do for you, sir?’

‘My name is Criminal Commissar Thomas Macke.’ He grabbed a passing waiter by the arm and said: ‘Bring me a coffee.’

The waiter looked enquiringly at Robert, who nodded.

‘I work in the political department of the Prussian police,’ Macke went on. ‘I am in charge of the Berlin intelligence section.’

Lloyd translated for his mother in a low voice.

‘However,’ said Macke, ‘I wish to speak to the proprietor of the restaurant about a personal matter.’

Robert said: ‘Where did you work a month ago?’

The unexpected question startled Macke, and he replied immediately: ‘At the police station in Kreuzberg.’

‘And what was your job there?’

‘I was in charge of records. Why do you ask?’