'I know,' said Tessa. 'I was talking to Fiona about him, and she says that Giles Trent was working with your lot in Berlin back in 1978. She says he's quite important.'

Fiona came in with the champagne and poured a glass for me. I said, 'Well, if that's what Fiona says…'

Fiona said, 'Tessa is my sister, darling. She's not going to go blurting out all your secrets to the Russians. Are you, Tess?'

'Not until the right Russian comes my way. Even then… I mean, did you ever see those photos of Russian ladies?' She held the pearl necklace in her mouth; it was a babyish gesture; she liked being a baby.

'What about Giles Trent?' I said.

Tessa toyed with the necklace again. 'I got to know him last summer. I met him at a dinner party given by some people who live down the road from us. He had tickets for Covent Garden – Mozart. I forget the name of the opera, but everyone was saying how difficult it was to get tickets, and Giles could get them. Well, it was heavenly. I'm not awfully keen on opera but we had a box and a bottle of champagne in the interval.'

'And you had an affair with him,' I finished it for her.

'He's a handsome brute, Bernie. And George was away watching the Japanese making motorcars.'

'Why not go with him?' I said.

'If you'd ever been on one of those trips that car manufacturers provide for the dealers, you wouldn't ask. Wives are superfluous, darling. There are hot and cold running girls in every bedroom.'

Fiona poured champagne for herself and Tessa, and said, 'Tess wants to tell you about Giles Trent. She doesn't want your advice on her marriage.' This admonition, like all such wifely admonitions, was delivered with a smile and a laugh.

'So tell me about Giles Trent,' I said.

'You were joking just now, I know. But Giles is older than you, Bernie, quite a bit older. He's a bachelor, very set in his ways. I thought he was queer at first. He's so neat and tidy and fussy about what he wears and what he eats and all that. In the kitchen – he has a divine house off the King's Road – all his chopping knives and saucepans are placed side by side, smallest on the left and biggest on the right. And it's so perfect that I was frightened to boil an egg and slice a loaf in case I spilled crumbs on the spotless tiled floor or marked the chopping board.'

Tell me how you first discovered he wasn't queer,' I said.

'I said he wouldn't listen to me,' Tessa complained to Fiona. 'I said he'd just make sarcastic remarks all the time, and I was right.'

'It's serious, Bernard,' said my wife. She only called me Bernard when things were serious.

'You mean it's wedding bells for Tessa and Giles?'

'I mean Giles Trent is passing intelligence material to someone from the Russian Embassy.'

There was a long silence until finally I said, 'Shit.'

'Giles Trent has been in the service a long time,' said Fiona.

'Longer than I have,' I said. 'Giles Trent was lecturing at the training school by the time I got there.'

'In Berlin he was in Signals at one time,' said Fiona.

'Yes,' I said. 'And he compiled that training report for interrogators. I don't like the sound of that. Giles Trent, eh?'

'Giles Trent doesn't seem the type,' said Fiona. All the ladies had a soft spot for the elegant and gentlemanly Giles Trent. He raised his hat to them and always had a clean shirt.

They never are the type,' I said.

'But no contact with field agents,' said Fiona.

'Well, let's be thankful for that at least,' I said. I looked at Tessa. 'Have you mentioned all this to anyone?'

'Only to Daddy,' said Tessa. 'He said forget all about it.'

'Good old Daddy,' I said. 'Always there when you need him.'

Mrs Dias came in bearing a large platter of shrimp fried in batter. 'Don't eat too many, sir,' she said in her shrill accent. 'Make you very fat.' The Portuguese are a lugubrious breed, and yet Mrs Dias was always smiling. I had the feeling that we were paying her too much.

'You're wonderful, Mrs Dias,' said my wife, smiling, although the smile faded when she recognized the shrimps as those she'd set aside in the kitchen to thaw for next day's lunch.

'She's a treasure,' said Tessa, taking a sample of the fried shrimp and burning her mouth so that she had to spit pieces of shrimp into her paper napkin. 'My God, it's hot,' she said, pulling a face.

Fiona, who hated anything fried in batter, waved a hand as I offered her the plate. I took one, blew on it, and ate it. It wasn't bad.

'We'll manage now, Mrs Dias,' said Fiona airily. I twisted round to see Mrs Dias standing at the door watching us with a big smile. She disappeared into the kitchen again. There was a cloud of smoke and a loud crash which we all pretended not to hear.

I said to Tessa, 'How do you know he's passing stuff to the Russians?'

'He told me,' she said.

'Just like that?'

'We'd started off in the middle of the afternoon drinking at some funny little club in Soho while Giles was watching the horses on TV. He won some money on one of the races and we went to the Ritz. We'd met a few friends by then, and Giles wanted to impress everyone by giving them dinner. I suggested Annabel's – George is a member. We stayed there late and Giles turned out to be a super dancer…'

'Is this all leading up to something he told you in bed?' I said wearily.

'Well, yes. We went back to this dear little place he has off the King's Road. And I'd had a few drinks, and to tell you the truth I thought of George with all those Oriental popsies and I thought, what the hell. And I let Giles talk me into staying there.'

'What exactly did he say, Tessa? Because it's nearly half past eight and I'm getting hungry.'

'He woke me up in the middle of the night. It was absolutely ghastly. He sat up in bed and howled. It was positively orgasmic, darling. You've no idea. He howled for help or something. It was a nightmare. I mean, I've had nightmares and I've seen other people having nightmares – at school half the girls in the dorm had nightmares every night, didn't they, Fi? – but not like this. He was bathed in sweat and trembling like a leaf.'

'Giles Trent?' I said.

'Yes, I know. It's hard to imagine, isn't it? I mean he's so damned stiff-upper-lip and Grenadier Guards. But there he was shouting and having this nightmare. I had to shake him for ages before he awoke.'

Fiona said, 'Tell Bernie what he was shouting.'

'He shouted, "Help me! They made me do it," and "Please please please." Then I went and got him a big drink of Perrier water. He said that was what he wanted. He pulled himself together and seemed all right again. And then he suddenly asked me what I'd say if he told me he was a spy for the Russians. I said I'd laugh. And he nodded and said, well, it was true anyway. So I said, for money, do you do it for money? I was joking because I thought he was joking, you see.'

'So what did he say about money?' I asked.

'I knew he wasn't short of money,' said Tessa. 'He was at Eton and he knows anyone who's anyone. He has the same tailor as Daddy, and he's not cheap. And Giles is a member of so many clubs and you know how much club subscriptions cost nowadays. George is always on about that, but he has to take business people out, of course. But Giles never complains about money. His father bought him the freehold of this place where he lives and gave him an allowance that is enough to keep body and soul together.'

'And he has his salary,' I said.

'Well, that doesn't go far, Bernie,' said Tessa. 'How do you imagine you and Fiona would manage if all she had was your salary?'

'Other people manage,' I said.

'But not people like us,' said Tessa in a voice of sweet reasonableness. 'Poor Fiona has to buy Sainsbury's champagne because she knows you'll grumble if she gets the sort of champers Daddy drinks.'