Not that he had any problem with beating up suspects. In his office at the back of the building he could hear the screams of men and women being tortured in the basement, but it did not bother him. They were traitors, subversives and revolutionaries. They had ruined Germany with their strikes, and they would do worse if they got the chance. He had no sympathy for them. He only wished Robert von Ulrich was among them, groaning in agony and begging for mercy.

It was eight o’clock in the evening on Thursday 2 March before he got a chance to check on Robert.

He sent his team home, and took a sheaf of updated lists upstairs to his boss, Criminal Inspector Kringelein. Then he returned to the files.

He was in no hurry to go home. He lived alone. His wife, an undisciplined woman, had gone off with a waiter from his brother’s restaurant, saying she wanted to be free. There were no children.

He began to comb the files.

He had already established that Robert von Ulrich had joined the Nazi Party in 1923 and had left two years later. That in itself did not mean much. Macke needed more.

The filing system was not as logical as he would have liked. All in all, he was disappointed in the Prussian police. The rumour was that Göring was equally unimpressed, and planned to detach the political and intelligence departments from the regular force and form them into a new, more efficient secret police force. Macke thought that was a good idea.

Meanwhile, he failed to find Robert von Ulrich in any of the regular files. Perhaps that was not merely a sign of inefficiency. The man might be blameless. As an Austrian count, he was unlikely to be a Communist or a Jew. It seemed the worst that could be said of him was that his cousin Walter was a Social Democrat. That was not a crime – not yet.

Macke now realized that he should have done this research before approaching the man. But he had gone ahead without full information. He might have known that was a mistake. In consequence, he had been forced to submit to condescension and sarcasm. He had felt humiliated. But he would get his own back.

He began to go through miscellaneous papers in a dusty cupboard at the back of the room.

The name of von Ulrich did not appear here either, but there was one document missing.

According to the list pinned to the inside of the cupboard door, there should have been a file of 117 pages entitled ‘Vice Establishments’. It sounded like a survey of Berlin’s nightclubs. Macke could guess why it was not here. It must have been in use recently: all the more decadent night spots had been closed down when Hitler became chancellor.

Macke went back upstairs. Kringelein was briefing uniformed police who were to raid the updated addresses Macke had provided of Communists and their allies.