'Calm down. Everyone knows Werner is your alter ego, and so mustn't be criticized.'

'What do you want? You can have "lean meat", "pure meat", "meat without fat" or "a bit of everything".'

'What's the difference between…'

'Don't let's get into semantics,' I said. 'Try surtido, that's a bit of everything.' Dicky nodded his agreement.

Dicky, who always showed a remarkable aptitude for feeding himself, now discovered that a carnitas stand is always conveniently close to those that sell the necessary accompaniments. He provided us with salsas and marinated cactus, and was now discovering that tortillas are sold by the kilo. 'A kilo,' he said as the tortilla lady disappeared with the payment and left him with a huge pile of them. 'Do you think they'll keep if I take them back for Daphne?' He wrapped some of the pork into the top tortilla. 'Delicious,' he said as he ate the first one and took a second tortilla to begin making another. 'What are all those pieces?'

'That's ear, and those pieces are intestine,' I said.

'You just wait until Daphne hears what I've been eating; she'll throw up. Our neighbours came out to Mexico last year and stayed in the Sheraton. They wouldn't even clean their teeth unless they had bottled water. I wish I had my camera so you could photograph me eating here in the market. Now what is it again – carnitas? I want to get it exactly right when I tell them.'

'Carnitas,' I said. 'Surtido.'

Dicky wiped his mouth on his handkerchief and stood up and looked round the market square. Just from where we were sitting I could see people selling plastic toys, antique tables and gilt mirrors, cheap shirts, brass bedsteads, dog-eared American film magazines and a selection of cut-glass stoppers that always survive long after the decanters. 'Yes,' said Dicky. 'It's really quite a place, isn't it? Fifteen million people perched at seven thousand feet altitude with high mountain tops all round them and thick smog permanently overhead. Where else could you find a capital city with no river, no coastline and such lousy roads? And yet this is one of the oldest cities the world has ever known. If that doesn't prove that the human race is stone-raving mad, nothing will.'

'I hope you don't think I'm going to walk right up to Stinnes and offer him a chance to defect,' I said.

'I've been thinking about that,' said Dicky. 'The Volkmanns already know him. Shall we let them make the first overtures?'

'Werner doesn't work for the department. You just told me that.'

'Correction,' said Dicky. 'I said that Werner's knowledge of Berlin is not sufficient reason for using him in Berlin. Let's remember that Werner has had a "non-critical employment only" tag on his file.'

'You can be a spiteful bastard, Dicky,' I said. 'You're talking about that signals leak in 1978. You know very well that Werner was completely cleared of suspicion.'

'It was your wife who did it,' said Dicky. Suddenly he was angry. He was angry because he'd never suspected Fiona of leaking secrets, and now I realized that Dicky saw me as someone who had helped to deceive him rather than as Fiona's principal victim.

The sky was darkening with clouds now and there was the movement of air that precedes a storm. I never got used to the speedy effects of the heat and humidity. The sweet smell of fresh fruits and vegetables had filled the air when we first arrived at the market. Now it was already giving way to the smells of putrefaction as the spoiled, squashed and broken produce went bad.

'Yes, it was my wife who did it. Werner was innocent.'

'And if you'd listened you'd have heard me say that Werner has had a "non-crit" tag on his file. I didn't say it was still there.'

'And now you're going to ask Werner to enrol Stinnes for you?'

'I think you'd better put it to him, Bernard.'

'He's on holiday,' I said. 'It's a sort of second honeymoon.'

'So you told me,' said Dicky. 'But my guess is that they are both getting a bit bored with each other. If you were on your honeymoon – first, second or third – you wouldn't want to spend the evenings in some broken-down German club in a seedy part of town, would you?'

'We haven't seen the club yet,' I reminded him. 'Perhaps it's tremendous.'

'I love the way you said that, Bernard. I wish I could have recorded the way you said "tremendous". Yes, it might be Mexico's answer to Caesar's Palace in Vegas, or the Paris Lido, but don't bank on it. You see, if it was me on a second honeymoon with that delectable little Zena, I'd be in Acapulco, or maybe finding some sandy little beach where we could be undisturbed. I wouldn't be taking her along to the Kronprinz club to see who's winning the bridge tournament.'

'The way it's turned out,' I said, 'you're not taking the delectable little Zena anywhere. I thought I heard you saying you didn't like her. I remember you saying that one honeymoon with Zena would be enough for you.' From the sulphurous yellow sky there came a steady drum-roll of thunder, an overture for a big storm.

Dicky laughed. 'I admit I was a little hasty,' he said. 'I hadn't been away from home for very long when I said that. The way I feel now, Zena is looking sexier and sexier every day.'

'And you think talking to Stinnes about Western democracy and the free world will give the Volkmanns a new interest in life,' I said.

'Even allowing for your sarcasm, yes. Why don't you put it to them and see what they say?'

'Why don't you put it to them and see what they say?'

'Look at those children and the donkey and the old man with the sombrero. That would make the sort of photo that wins prizes at the Photo Club. I was so stupid not to bring a camera. But have you seen the sort of price you have to pay for a camera in this country? The Americans are really putting the squeeze on the peso. No, I think you should put it to them, Bernard. You get hold of Werner and talk with him, and then he could go along to the Kronprinz Club tonight and see if Stinnes is there.' He stopped at a stall to watch a man making chiles rellenos, putting meat fillings into large peppers. Each one got a big spoonful of chopped chillies before being deep-fried and put in a garlicky tomato sauce. Just looking at it made me feel queasy.

'Werner will have to know what London is prepared to offer Stinnes. I assume there will eventually be a big first payment, a salary and contractual provisions about the size of the house they'll get and what sort of car and so on.'

'Is that the way it's done?' said Dicky. 'It sounds like a marriage contract.'

'They like it defined like that because you can't buy houses in East Europe and they don't know the prices of cars and so on. They usually want to have a clear idea of what they are getting.'

'London will pay,' said Dicky. 'They want Stinnes; they really want him. That's just between us, of course; that's not for Werner Volkmann to know.' He touched the side of his nose in a conspiratorial gesture. 'No reasonable demand will be refused.'

'So what does Werner say to Stinnes?' On the cobbled ground there were shiny black spots appearing one after the other in the grey dust. The rain had come.

'Let's keep it all very soft-sell, shall we?' said Dicky. His wife Daphne worked in a small advertising agency. Dicky told me that it had very aggressive methods with really up-to-date selling techniques. Sometimes I got the feeling that Dicky would like to see the department being run on the same lines. Preferably by him.

'You mean we don't brief Werner?'

'Let's see how the cookie crumbles,' said Dicky. It was an old advertising expression that meant put your head in the sand, your arse in the air and wait for the explosion.

My prediction that the rain came only in the afternoons was only just right. It was a few minutes after one o'clock when the rain started. Dicky took me in the car as far as the university, where he was to see one of his Oxford friends, and there – on the open plaza – let me out into steady rain. I cursed him, but there was no hostility in Dicky's self-interest; he would have done the same thing to almost anyone.