'Secrecy is of paramount importance? And you've left a message with the night-duty officer at Five? You realize that probationers – kids just down from college – are likely to get weekend duties like that. Whoever he is, he'll want to cover himself, so now he's phoning everyone in his contact book and trying to think of more names.'

'You're becoming paranoid, Bernard,' Bret said. He smiled to show me how calm he was remaining. 'Even if he is an inexperienced kid from college – and I know kids from college are not high on your all-time Hit Parade – the messages he'll leave with maids, au pair girls and receptionists at country hotels won't explicitly describe our operation.'

He was a sarcastic bastard. 'For God's sake, grow up, Bret,' I said. 'Can't you see that a flurry of activity like that – messages being left in all sorts of non-departmental places for the urgent attention of senior MI5 staff – is enough to compromise your operation?'

'I don't agree,' he said, but he stopped smiling.

'Some smart newspaper man is likely to get the smell of that one. If that happens, it could blow up in your face.'

'In my face?'

'Well, what are those messages going to be saying? They are going to be saying that we're just about to go blundering into matters that don't concern us. They're going to say we're stealing Five's jobs from them. And they'll be right.'

'This isn't a hot tip on a horse; they'll be sensible,' said Bret.

'It's going to be all over town,' I said. 'You're putting your man into danger, real danger. Forget it.'

'Ml5 are not going to let newsmen get hold of secrets like this.'

'You hope they're not. But this isn't their secret, it's ours. What will they care if your Boy Scout comes a cropper? They'll be delighted. It would teach us a lesson. And why would they be so fussy about newspaper men getting the story? If it made headlines that said we were treading on their territory, it would suit their book.'

'I'm not sure I want to listen to this any more,' said Bret huffily. This was Bret getting ready for his knighthood – loyal servant of Her Majesty and all that. 'I trust MI5 to be just as careful with secret information as we are.'

'So do I, if it's their information. But this is not their information. This is a message – a message from you; not a message about one of their operations but about one of ours. What's more, it was given out on a Friday evening in what is a transparent trick to hamper any efforts they might make to stop us. How can you believe they'll play it your way and help you score?'

'It's too late now,' said Bret. He took two ice cubes from a container that was painted to look like a side drum from the band of the Grenadier Guards, complete with battle honours, and dropped them into his drink. Bret could make one drink last a long time. It was a trick I'd never mastered. He offered ice to me but I shook my head. 'It's all approved and signed for. There's not going to be any pussyfooting about trying to infiltrate them. There's an office in Cambridge which contains files on the whole network. It's coded, Stinnes says, coded to read like normal office files. But that shouldn't be a big problem. We're putting a man in there this evening. He's coming here to meet you.'

'Beautiful, Bret,' I said sarcastically. 'That's all I need – for your tame gorilla to get a good look at me before he gets rolled in a carpet and shipped to Moscow.'

Bret permitted himself a ghost of a smile. 'It's not that kind of operation, Bernard. This is the other side of the job. We'll be in England. If there's any interference, we'll be putting the handcuffs on those bastards, not the other way around.'

I weakened. I should have remained cynical about it, but I weakened because I began to feel that it might prove as simple as Bret Rensselaer said it would be. 'Okay. What do you want me to do?'

'Run him up to Cambridge and play nurse.' So that was it. I should have guessed that you don't get invited to Bret's for nothing. My heart sank into my guts. I felt the way some of those girls must have felt when they realized there were more works of art that lined the stairs all the way to Bret's bedroom. He saw it in my face. 'Did you think I was going to try to do it myself?'

'No, I didn't.'

'If you really think I can do it, Bernard, I'll try.' He was restless. He got up again and poured more gin for me. It was only then that I realized that I'd gulped the rest of my drink without even noticing that I'd done so. 'But I think our man deserves the best help we can find for him. And you're the best.'

He went back and sat down. I didn't reply. For a moment we both sat there in that beautiful room thinking our own thoughts. I don't know what Bret was thinking of, but I was back to trying to decide what his relationship with my wife had been.

At one time I'd felt sure that Fiona and Bret had been lovers. I looked at him. She was right for him, that very beautiful woman from a rich family. She was sophisticated in a way that only wealthy people can be. She had the confidence, stability, and intellect that nature provides for the first-born child.

The suspicion and jealousy of that time, not so long ago, had never gone away, and my feelings coloured everything I had to do with Bret. There was little chance I would ever discover the truth of it, and I was not really and truly sure that I wanted to know. And yet I couldn't stop thinking about them. Had they been together in this room?

'I'll never understand you, Bernard,' he said suddenly 'You're full of anger.'

I felt like saying that that was better than being full of shit, but in fact I didn't think that of Bret Rensselaer. I'd thought about him a lot over the past few months. First because I thought he was jumping into bed with Fiona, and now because the finger of treason was pointed at him. It all made sense. Put it all together and it made sense. If Bret and Fiona were lovers, then why not co-conspirators too?

I had never faced an official enquiry, but Bret had tried to make me admit that I'd been in league with my wife to betray the Department's secrets. Some traces of the mud he'd thrown had stuck to me. That would be a damned smart way to cover his own tracks. No one had ever accused Bret of being a co-conspirator with Fiona. No one had even suspected that they were having a love affair. No one, that is, except me. I had always been able to see how attractive he'd be for her. He was the sort of man I'd had as rivals when I'd first met her; mature, successful men, not Oxbridge graduates trying to hack a career in a merchant bank, but men much older than Fiona, men with servants and big shiny cars who paid for everything by just signing their name on the bill.

It was very dark in the room now and there was a growl of thunder. Then more thunder. I could see the clock's brass pendulum catching the light as it swung backwards and forwards. Bret's voice came out of the gloom. 'Or is it sadness? Anger or sadness – what's bugging you, Samson?'

I didn't want to play his silly undergraduate games, or sophisticated jet-set games, or whatever they were. 'What time is this poor bastard arriving?' I said.

'No fixed time. He'll be here for tea.'

That's great,' I said. Tea! Earl Grey no doubt, and I suppose Bret's housekeeper would be serving it in a silver teapot with muffins and those very thin cucumber sandwiches without crusts.

'You talked to Lange,' he said. 'And he bad-mouthed me the way he always does? Is that it? What did he say this tune?'

'He was talking about the time you went to Berlin and made him dismantle his networks.'

'He's such a crook. He's still resenting that after all these years?'

'He thinks you dealt a blow to a good system.'

The "Berlin System", the famous "Berlin System" that Lange always regarded as his personal creation. It was Lange who ruined it by bringing it into such discredit that London Central sent me there to salvage what I could from it.'