Müller was about to ask a question, but it died in her throat as she noticed – as Bahlow held her gaze in the rear-view mirror – the moisture gathering in his eyes.

‘Fearsome, massive bombing raids, barbaric bombing raids, in which I lost both my parents.’ There was a pause, as Bahlow tried to compose himself, his voice choking with his own memories and bitterness. After a moment, he continued. ‘To Southwick, this was proof of a war crime – and that Winston Churchill, his chief scientific adviser, Frederick Lindemann, and the head of bomber command, Arthur Harris, were all guilty. They were all war criminals. He wanted a case brought against them – or at least against the only remaining survivor – Bomber Harris.’

‘Why was that enough to get him killed?’ asked Tilsner. ‘The Nazis started the war, they lost, how would any war crime trial have succeeded?’

‘It probably wouldn’t,’ conceded Bahlow. ‘That’s not the point. The British government didn’t want their war heroes’ names blackened.’

Müller was aware of her eyes widening in disbelief as Bahlow continued his account. How he himself was assigned to the case when the Republic apparently wanted Southwick’s research strengthened. How he was told to use his contact, Lotti Rolf, to introduce Southwick to a Russian who would produce more secret documents – proving that Churchill ignored a request by Stalin not to bomb Dresden because of all the refugees there.

Tilsner gave a disbelieving laugh. But Bahlow simply acknowledged it by agreeing that it should have made him suspicious. Why would someone like Stalin care about something like that? Nevertheless, he explained, he had a personal interest – because of what had happened to his parents – in making Southwick’s research paper as strong as possible and for the truth to be revealed about the Dresden bombings.

‘The only trouble was, the Russian documents were fakes – and easily proved to be fakes.’

‘I don’t understand,’ said Müller.

‘It was a deliberate ploy by my superiors in the Ministry for State Security to wreck Southwick’s research,’ said Bahlow, apologetically.

He went on to explain how Britain and the Republic had come to an arrangement. How initially, the Republic saw Southwick’s paper as a way to extract money from Britain in the way of reparations to help with the country’s hard currency crisis. When the Stasi high-ups came to realise that wasn’t going to happen, someone had the brighter idea of helping to suppress Southwick’s findings – and the genuine documents about the psychological study – by providing him with more fake documents. These were the Soviet documents about Stalin. Bahlow claimed the aim was to destroy Southwick’s entire reputation, as well as discredit his research, in exchange for a rather large sum of hard currency from Britain.