It clearly is my signature. If it’s a forgery, even I couldn’t detect it. ‘But I never signed anything with the Ministry for State Security.’

‘Unfortunately,’ says Breitmann, ‘it’s here in black and white.’

I don’t want to play their game, but this all must be leading somewhere. I sigh. ‘What exactly is it you want?’

‘Where is your final research document?’ asks Breitmann. ‘The rewritten one. The one you changed after the first draft was rejected for containing fake sources.’

‘I don’t know what you’re talking about.’

The crack of the gun butt against my temple comes from nowhere, sending me spinning, dazed, onto the concrete floor. Incredible pain daggers through my head.

‘We’re not in the mood to play games, Dr Southwick,’ says the colonel, as he turns the gun over in his hands, almost as though he’s worried he’s damaged it from the force of the blow.

I’m still holding the side of my head, bracing my body for the next blow. It doesn’t come. Instead, Breitmann has climbed onto the bed. He’s tying some sort of material round the bare pipe that runs across the ceiling and down to the corner sink.

Specht is meanwhile getting something else from his briefcase. ‘We thought you might like these souvenirs of your stay in Dresden,’ he says.

They’re black and white photographs. Taken – I realise with horror – by a surveillance camera in my university apartment in Leningrader Straße.

I’m lying on my back on the bed.

My hands on Lotti’s head.

Hands which – in my memory – had been trying to pull her mouth away from my erect penis after I’d woken up in horror to find her in my bed.

But hands which, here in the photographs, appear to be holding her head down, encouraging her.

Breitmann has finished whatever he was doing with the material and water pipe. ‘Your wife – Barbara, isn’t it? – she’ll be a bit taken aback by what you’ve been up to, old chap. Not the sort of research wives tend to approve of, is it?’

I struggle to my feet, try to lunge at him, but Specht holds me firm, pulling my arms up behind my back.

‘Now, now, Dr Southwick. Don’t do anything rash,’ he hisses into my ear. ‘Just tell us where your rewritten research paper is, and where the original documents are.’

‘What documents?’ I bluster.

This time it’s Breitmann that answers. ‘The ones given to you by Lindemann’s former secretary during your cosy chat at the Lyceum Tavern last summer. They are British government property.’

I feel something pushing against my bruised temple. From the corner of my eye, I can see it’s the gun.