Then, as Müller stifled a gasp, Bahlow delivered his killer line – revealing who their Concrete Man was, knowledge he’d obviously had for some time, while Müller and Tilsner had been chasing their tails to try to unravel the mystery.

‘The man who was killed here, in Gorbitz, was supposedly the “Russian” supplying the fake documents – although my information is that he was a fairly lowly Stasi operative suckered into doing it for a cash backhander. He’s the one who lost his life – in an argument with Southwick and Lotti Rolf that appears to have gone sour.’ If Müller and Tilsner now accepted Bahlow’s account, it was Lotti Rolf who wielded the near fatal blow, although Bahlow’s view was that she wasn’t deliberately trying to kill the man. It was more a case of protecting Southwick.

‘But I was duped as well,’ insisted Bahlow. ‘That’s when I began helping you two. When I found out.’

‘Why should we believe you?’ asked Müller.

‘I’ve already seen you looking into my eyes, Karin,’ said Bahlow, adjusting the rear-view mirror so that their eyelines met again.

Müller could see the previous moisture had become fully formed tears. They could be crocodile tears, of course, but she didn’t think so. If Bahlow had indeed lost both his parents in the Dresden firebombing, and Müller had no reason to doubt that, then of course he would have a burning desire for the truth to come out – even after all these years.

‘So what happens now?’ asked Müller. She realised they’d reached Gorbitz, and Bahlow had parked where Concrete Man’s body had been discovered, just a few days earlier at the start of all this.

‘That’s up to you two,’ said Bahlow. ‘I saw that Southwick tried to whisper something to you, just before he died. The Stasi and the British know that he rewrote his research, omitting reference to the Soviet documents. They are both determined to get hold of that and destroy it. I suspect the reason we found him swinging there in his cell is that he wouldn’t tell them where it is. If he’s told you, it’s on your conscience what you do with it. I very much hope that – somehow – it sees the light of day. But you can be sure if my colleagues in the Ministry for State Security or the British get hold of it first, it won’t. And if they know you’ve got it, I’m afraid it’s your lives that will be in danger.’

Müller was tempted to wait until Bahlow had disappeared before trying to follow Southwick’s whispered instructions. There was only one pub that had so far been built in Gorbitz – the ubiquitous Zum grüner Heinrich – and Müller already knew that was where the housing estate’s foundation stone lay too – in the pub’s wall.