‘Because we’re not sure who they are. Mr Borisov is or was a member of the Russian intelligence service SMERSH, and he has a great deal of information on them, but he has only ever known them by their code names. We are hoping by intensive questioning and deduction that we will be able to narrow down our search for the traitor. In the meantime, I have to keep him safe. Tom and I are the only two who know he has defected. Actually, you make that three now.’

‘Well, keep him in your own house, Philip. You have a lovely home in Chelsea – survived the Blitz, didn’t it?’

‘There’s another matter, of course. As you pointed out, the Soviet Union is our ally. If they hear we have Borisov here, they will demand his return and we will be obliged to comply. We can’t allow that.’

‘You didn’t answer my question.’

‘How’s that coffee coming along? You know, I could keep you jolly well supplied. I wouldn’t expect you to do this for nothing.’

‘You sound like a bloody black marketeer.’

He shrugged with a guilty smile.

‘Does Tom know about this plan?’

‘I can’t make contact with him at the moment. Do you think he’d object?’

‘The question, really, is whether I object, isn’t it?’

‘Yes, of course.’

Sergei Borisov put his fat, rough hand on the table. ‘Please, Mrs Wilde, I realise this is asking a great thing of you and I will understand completely if you turn me away. There will be no hard feelings. But allow me to tell you a bit about myself. I studied at Cambridge before the war – the first war, that is. As you can see, I am not a young man. I know and love this town very much and it is my heartfelt desire to teach here one day, if one of the colleges would accept me. But in the meantime, I am homeless and I badly need a bed for a few nights. I promise I would be no trouble to you or your son. I would add that I did your husband a very great favour in Berlin, and one day I am sure he will confirm that to you.’

She looked at Eaton and shook her head in resignation. She knew when she was beaten. ‘How long is a few nights, Philip?’

‘No more than a week. This has all been done in an immense hurry, but I will find a suitable place for Mr Borisov sooner rather than later, I promise you.’ His eyes strayed to the letter on the table.

‘Read it if you like,’ she said. ‘Or burn it.’

‘I confess I noticed the Bart’s heading.’