'Like stock. You sound like some awful Nazi geneticist.'

'Oh bollocks, Monica, everybody knows the bloody Indians and Chinese are good at maths,' Rupert snapped, 'just like black blokes make the best boxers.'

'Shut up, Rupert,' Laura said angrily. 'I mean it. It's not funny. It's bloody offensive.'

'Yes, it is!' Jane echoed. 'And quite honestly, Rupert, if you carry on like that you're going to have to go.'

'And as to you, Jimmy,' Rupert continued, ignoring Laura and Jane completely, 'and your ridiculous efforts to turn this into a class issue, the trading floors are full of comprehensive school kids.'

'Ah yes, the famous new breed of Cock-er-ney barrow boys,' Henry said snootily.

'Who almost exclusively remain at floor level,' said Jimmy. 'Don't see a lot of them in the boardroom, do we, Roop? And I doubt there's any challenging you on the ladder at the Royal Lancashire.'

'It's irrelevant anyway,' Rupert insisted, 'because that is not the point. The point is that those kids haven't had the advantages we've had and are therefore of no interest to a major private bank or brokerage. Personally, I would contend that "advantage" as you call it is merely another word for Darwinian natural selection-'

At this the whole room erupted into a chorus of liberal outrage.

'For Darwinian natural selection,' Rupert ploughed on loudly. 'The bank employs the people it feels will give it the most significant advantage in the workplace and pays them according to their market value. It's as simple as that. If there were hundreds of other people who could do those jobs their value would decline and they would be paid less. It's the rules of economics.'

'Look, Rupert,' Henry said, trying to sound measured and authoritative, 'I can see that you're being deliberately provocative but I think this is a serious enough issue for adult debate, don't you?'

'Blimey, Henry,' Jimmy said, smiling, 'you sound exactly like you used to when you were trying to stop me drinking your milk out of the fridge and nicking your chocolate.'

'And this is an issue of equal national importance,' Henry replied, smiling also. 'Rupert, you simply cannot claim that the preponderance of posh kids in the upper echelons of banking is due to some genetic advantage. I chair the parliamentary committee on social mobility and I know that your profession is a private members' club and you make your own rules.'

'Tell me, Henry,' Rupert enquired, dipping a spring roll in the chilli sauce, 'how many MPs are there these days in the Parliamentary Labour Party who were born into the working class?'

For a moment Henry looked flustered and was of course rewarded with a chorus of good-natured catcalls.

'I think you'll find, Henry,' Rupert continued, 'that the Darwinian law of survival of the richest and best educated applies to all professions, including yours. It's simply that some of us aren't hypocrites about it.'

Henry was clearly thinking furiously and Amanda took the opportunity to press home Rupert's advantage. She might have issues with his working hours and choice of the most attractive PAs, but when it came to reactionary economic theory Rupert and Amanda were a team.

'Come on, Henry,' she said, ''fess up. How many Labour MPs are there who aren't from the much-maligned middle class?'

'As it happens, Rupert,' said Henry, 'we search constantly to find new candidates from every under-represented group. Female candidates. Ethnic candidates . . .'

'I'm not talking about sex or race, Henry,' Rupert interrupted. 'I know you'll bend over backwards for a disabled black homosexual.'

'Woof woof!' Robbo shouted.

'Shut up, Robbo,' Lizzie scolded. 'That was so predictable.'

'I'm talking about class and money. Your entire party is more middle class now than it has ever been. You don't represent social mobility at all. You represent social stagnation.'

Henry was furious, that was clear, but he had no answer to Rupert and Amanda's point so he moved the goalposts.

'Well, to be honest, when I see how you and Jimmy live, Rupert, I realize I'm an absolute arse to care about politics or improving people's lives at all. What I should be doing is buying up successful banks, sacking all their staff and pocketing the savings.'

'Not jealous, are we, Henry?' Amanda enquired archly.

'Of course I'm bloody jealous,' Henry snapped back. 'It's bloody stupid. The money you earn makes everyone else look like a pauper! I'm an assistant chief whip, for God's sake. I'm tipped for the Cabinet, yet I doubt I make a tenth of what Jimmy bloody earns and he's an arse.'

'Never denied it.' Jimmy smiled but he didn't comment further. He wasn't sure what the difference was between his and Henry's income but he imagined that he might earn a bit more than ten times his friend.

'Nobody makes what you guys make,' Henry went on. 'Doctors, senior police officers, BBC execs, top council employees, politicians like me, all sorts of people who are responsible for the well-being of thousands earn a fraction of what a lucky little bastard like Jim earns. No offence of course, Jimmy.'

'None taken, Henry. If I were you I'd be jealous.'

'I'm not fucking jealous!' Henry shouted, contradicting himself. 'I'm outraged.'

'But actually I think you should be grateful about how much I earn, mate,' Jimmy said and, as so often with Jimmy, it was difficult to see how seriously he intended himself to be taken.

'So how does that work then?' David asked. 'I mean I don't mind earning more than Henry but I don't expect him to be grateful.'

'Well, think about it,' said Jimmy. 'OK, Henry doesn't make what I earn but he does all right, thank you very much. What is it now for an MP? About sixty grand a year? Plus all those expenses, this second home allowance thing. Got to bring it up to eighty at least, I'd say. Probably a hundred.'

'Oh please, Jim,' Monica said with some distaste, 'let's not start comparing incomes.'

'I'm not comparing anything. I'm just saying my guess is that in relative terms Henry makes at least twice what an MP would have made a generation or two ago. It's the same with all the other jobs you mentioned. Cops, councillors, doctors. BBC broadcasters. They all earn a much higher multiple of the average wage than they used to. In the fifties and sixties doctors weren't seriously richer than their patients, council bosses didn't think they should be paid umpteen times what the tenants they worked for made. BBC programmers didn't expect to be massively richer than the viewers. But they do now. They all expect much more money. Well, we've done that for you, mate. People like me and Rupert. Because whenever people say you make too much money, you say, "Look at those bastards in the City." It's the trickle-down. You look at our obscene bonuses and think that your merely very generous salaries pale in comparison, but remember that it's only because our bonuses are obscene that your salaries are so generous. Everyone's following our example. In the post-boom-and-bust world, if you take jealousy out of the equation everybody wins. Unless you're a member of the underclass, of course.'

There was a moment's silence. People weren't used to Jimmy doing anything but crack gags and chuck bread about. Perhaps he was joking now.

'Do you ever feel guilty about it, Jimmy?' Robbo asked suddenly. 'I mean about just how rich you are? I know Lizzie and I used to but . . . I don't any more . . . Why should we? I mean we've earned it, haven't we?'

'I find you get used to money,' Jimmy replied. 'Like when you have nothing you think you'd be happy with a tenner and that the bloke with a hundred is a total bastard. Then when you've got the tenner you start to think a hundred is fair but a thousand would be obscene. Then you get a thousand and suddenly that's all right too. Henry makes plenty compared with 90 per cent of the people he represents but he thinks that's OK, in fact he should get a bit more. It's us he thinks are taking the piss.'

'Yes I do, as it happens,' Henry replied.

'Look, Henry,' Robbo said, 'it's all very well for you to be snooty and pious. You don't have to deal with this sort of dilemma. You do an important job and you make a decent wage. That's great. Everybody's happy. I, on the other hand, married a genius who ended up inventing and running her own very successful business.'

'And that's a problem for you?' Jane asked.

'Well, in a way I suppose it is,' Robbo insisted. 'I mean I'm not like Rupert. I never expected to be this rich, nor did Jim. But when you become this rich, what do you do? Do you give it away? Would you?'

'Well, not all of it, I suppose,' Henry conceded.

'If not all, then how much?' Robbo pressed. 'Actually what happens is you end up just getting used to being that wealthy so you begin to think that that's the norm. That it's kind of logical and inevitable and right that you should have that much money.'

'Yeah,' Jimmy agreed. 'If I'd jumped from my first year's income to what I'm earning now I truly would have thought that the world had gone mad and that it was obscenely unfair, but because it just grew I don't find it that way at all.'

'Except of course it is obscene and deep down we know it,' said Robbo, 'and that's why I sort of envy you not having to worry about it, Henry.'

'My heart bleeds for you,' Henry replied drily.

'What I don't understand,' Monica said, 'is where all this money is coming from.'

Rupert rolled his eyes in a pantomime of indulgent frustration.

'Everybody asks that,' he said. 'Why? Why do they care as long as it's there? Why worry about where it's coming from?'

'Well, I'm certainly not complaining!' Monica hastened to add.

And with that, more wine was opened and Rupert went on to explain in some detail how the more he was paid, the better it was for the economies of emerging nations.

Nappy economics 'The wheels on the bus go round and round. Round and round. Round and round,' he sang, as he always did when changing Lillie. He reached into the enormous plastic Pampers sack, which for a panicky moment he thought was empty. It wasn't, there were three or four left in the bottom . . . A day's worth, for sure. But what then? Jimmy knew that they would have to buy more. He also knew that he would not be buying a bag of a hundred as he had done in the past, but a much smaller number.

Those two remaining credit cards had their limits and the day was fast approaching when those limits would be reached. It was a false economy to buy the small bags but Jimmy had by this time got used to the fact that the less money you had, the fewer options you had to spend it efficiently.

Nobody could understand how anybody living in a house like his could actually be at the point of counting pennies. Such a house could surely be mortgaged for millions. The problem was it had been mortgaged for millions already, to pay for Webb Street.

Jimmy had done it when he was rich.

He had done it in order to get richer. Exposing himself horribly in the process, under the impression that his salary and bonuses would always be there to pay the interest on the loan.

Jimmy's dad had warned him.

'Never use your house as collateral, son,' he had said. 'It's risking the seed corn.'

At the time Jimmy had thought that kind of thinking was exactly why his father's home was worth three hundred thousand while his was valued at seven million. Now of course he understood. His father still owned his house while he was calculating the cost of nappies. Of course with Lizzie riding to the rescue things were nothing like as bleak as he'd feared, but it was still going to be a very tough year.

'Lillie's fine. No poo,' Jimmy said, having pulled apart the Velcro.

And now he faced a dilemma. An appalling, shameful and ridiculous dilemma. There was no poo, it was true, but there was plenty of wee. Not so much that the nappy was a great bulging heavy sausage but certainly enough to activate whatever it was in the plastic which drew in the moisture and caused it to swell.

That was the dilemma. The nappy was not completely full; heavy, yes, but not so full as to be saturated. Should he change it? Should he spend eighteen pence immediately or rewrap it and wait until a change was absolutely essential? And it wasn't just eighteen pence, it was much more than that really because the next lot of nappies would be bought on his Visa or his MasterCard and he knew that this debt would not be paid off at the end of the month. The nappies that Lillie soiled with such frequency might be disposable but the debt they incurred would continue to grow at 13 per cent, possibly for as long as it would take the damn things to biodegrade. Jimmy had always considered himself a pretty green sort of guy, but these days he didn't give two fucks about any aspect of disposable nappies except what they cost.

He changed the nappy. Of course he changed the nappy. He was Jimmy Corby and he didn't care how much trouble he was in, his daughter could have a dry flipping bottom and a nice clean nappy. He owned a street, for God's sake, a street which with Lizzie and his dead friend's help he was now going to be in a position to hang on to.

Lillie immediately shat in the new nappy. That was her favourite trick, always had been. To wait until you'd cleaned her off, until you'd rubbed in the zinc cream, dusted on the powder and secured a new nappy, and then poo straight into it. The little baby girl gurgled happily as Jimmy changed her for a second time. It wasn't her fault, she could not possibly know that had she moved her bowels thirty seconds earlier (or had Jimmy waited for that time), he could have saved eighteen pence plus interest.

Jimmy put Lillie back on to her little padded mat with the dangly things above it and realized what it was that Monica had smelt when she thought Lillie needed changing.

'Cressida's done one on the floor,' he said.

'Oh grosseramma!' Toby said, looking up from his cereal.

'Well, what do you want me to do about it?' Monica replied, clingfilming a plain HobNob for Toby's midmorning treat. Toby had given up asking if there were any Muller Corners, having finally come to understand that there weren't. He told his friends he preferred HobNobs, particularly the plain ones as the chocolate ones were too sweet.

'You know the drill,' Monica continued, 'I read you the book. Put the poo in the potty and show it to her. You have to show her the poo in the potty and make appreciative noises. Then put her back on the potty.'

'I know the bloody theory,' Jimmy said, getting some toilet paper and picking up the turd, 'but it's not bloody working, is it?'

'It's not working because we're not consistent!' Monica replied angrily. 'That's the most important point of all. The book says you have to be consistent.'

'Bugger the book!'

'Don't say bugger, Daddy. It's swearing,' said Toby.

'I didn't, I said bother.'

'No you didn't, that doesn't even rhyme,' Toby insisted, drinking the milk from the bottom of the cornflakes bowl.

'You know the theory,' said Monica.

'Yes, Mon! I know the theory.'

Both their tempers were rising now.

'Well, bloody well apply it then!' Monica said, suddenly snapping. 'Children need routine. You can't keep changing the rules. It says in The Big Happy Baby Book that-'

'You know what?' said Jimmy. 'Screw The Big Happy Baby Book. That book is fiction! It's written by a childless fantasist. I have shown Cressida a hundred turds! I've cooed over them, admired them, sung to them, pinned medals on them, placed them back in the potty on velvet cushions and stuck her on top of them and the little bitch still prefers to shit on the floor. All right?'

Monica began to weep.

'Shut up!' she cried. 'Shut up, Jimmy! I can't stand it. I really can't. We have to try. We can't just . . .'

She had been pulling a jumper down over Toby's head as she broke down and when his little face emerged he was crying too.

'Don't worry, baby. Mummy's just being silly,' Monica croaked. 'We need a brush, Jimmy. Look at his hair. Don't cry, baby, please don't cry.'

Cressida and Lillie were wailing too. Jimmy wasn't, but only on the outside. Inside he was crying as well and as he cried inside it occurred to him yet again that he had once more forgotten that Robbo was dead.

His best friend was dead and he couldn't find a hairbrush. Could life get any harder?

'Oh God,' Monica said through her tears as she inspected Toby's head, 'he's got nits.'

'Can't worry about that now,' Jimmy said, sticking a bit of toast between his teeth, shoving the makeshift grandpa project into Toby's fist and grabbing his sports kit.

'Try not to scratch your head, darling,' Monica called after them as they headed for the lift that connected the family room with the garage beneath it. 'I'll put conditioner on it and comb them out tonight.'

A lift. A lift.

Jimmy was counting the cost of single nappies and yet he still owned and operated a private elevator. Jimmy had never been exactly sure what the word 'surreal' meant but he imagined that a jobless, penniless, debt-ridden loser taking a lift to his private underground car park might fit the bill.

Underfloor parking When Jimmy and Monica had bought their last and finest Notting Hill house in 2003 it had had ample room to park three cars in a large area at the front. Indeed this had been one of the features about which the estate agent was most enthusiastic.

'Look,' the agent had said conspiratorially, 'don't say I said it but you could probably service the interest on your mortgage renting out one of your parking spaces. The parking problem in London is out of control. I mean they bang on and on about the homeless, but actually there are a lot less people with nowhere to sleep than people with nowhere to park, and they need help too.'

The first thing Jimmy and Monica did with the parking area was get rid of it.

It was Lizzie's idea. She took one look at the front of the house and very forcefully explained to Monica and Jimmy that it simply wouldn't do. Such an arrangement was ridiculous, insane even. Here they were, Lizzie insisted, the owners of one of the loveliest detached town houses in Notting Hill, a house which by some quirk of Georgian architectural caprice was set much further back from the road than the other houses in the street, and yet the previous owners had seen fit to squander this precious feature and use it as a place to store their bloody cars.

'Vandals!' Lizzie had pronounced. 'People who cannot appreciate beautiful things should be banned by law from owning them.'

She stood on the granite-paved surface between the big new family Range Rover and Monica's spunky little Mini convertible and spread her arms wide.

'I shall tell you what this is,' she said dramatically. 'This, Monica, is your front garden.'