'CAN YOU afford it, boy?' Happily installed at the lunch table last Tuesday, Kingsley Amis reproduces in an immaculate Welsh lilt the response of the waiter when he ordered a bottle of Veuve Clicquot for himself and his wife Hilly at the Bush pub and restaurant in Swansea on the night of January 25, 1954, exactly 40 years to the day, earlier.

Not very easily on an English lecturer's salary, Amis might have answered the waiter. But that night was special. Gollancz had published Amis's first novel, Lucky Jim, the same day, thus launching a revolution in English fiction. A week earlier Hilly had given birth to their third child, Sally. If they could not push the boat out then, when could they?

Forty years and 23 novels later, many things have changed. Now Amis can effortlessly afford to eat and drink whatever he wants. He has long given up teaching for writing and he lives in London, not Swansea. Hilly and he, after various marital misadventures, again live in the same house, though the set-up is rather different. 'Like something out of an Iris Murdoch novel,' as Amis puts it. Hilly lives in the basement flat with her third husband, Lord Kilmarnock, while Amis occupies the two floors above. Relations are amazingly amiable. There is much coming and going between floors and Hilly is a welcome member of the party for a 40th anniversary celebration.

This is to take the form of lunch at Simpson's in the Strand. Lunch is now Amis's preferred meal. He never liked dinner parties and at 71 feels the freedom of age to turn down such invitations, except for his weekly encounter with his son Martin, the Amis who now first springs to many people's minds at the mention of the word novelist. Comparisons of this kind are apt to turn Amis senior stony-faced - parental and literary pride jostling across his expressive features to reach a sort of sourpuss deadlock - so we avoid making them.

The three of us gather for a preliminary large one at the Amis home in Primrose Hill, savouring the prospect of lunch as we wait for the taxi. Simpson's is an obvious choice, specialising as it does in traditional no-nonsense English dishes. This is the style Amis prefers in most things, in fiction as in food. According to his robust rule, there should be no experimental tomfoolery in either and anyone who thinks otherwise is an ass or a snob, or both.

Arrived at Simpson's, we head for the bar and two more large malt whiskies. Drink, I begin to sense, is going to account for the larger part of the bill, as indeed it turns out to do. At times like these the Amis lifestyle can seem a touch self-indulgent. If he was not here at Simpson's he would be sure to be lunching out, most likely at the Garrick Club, where he makes something of a point of being last to leave the bar and head downstairs for lunch.

Looked at another way, though, the Amis lifestyle takes on the improbable air of a rigorous schedule. Before lunch he will have pounded the typewriter for three hours. There will be another hour or two of work afterwards, between the post-luncheon snooze and evening drinks, followed by supper and Coronation Street or The Bill. Socialising in club or restaurant is a necessary part of the Amis regime, both reward for his labours and indispensable means of renewing his literary energies.

Now we leave Simpson's bar and go upstairs to the restaurant. Amis orders Cock-A-Leekie soup and fish and chips, then concentrates on the wine list, settling for a bottle of Beaujolais and another of Brouilly to follow. Do I notice the merest hint of raised eyebrows when the waiter addresses him as Mr Amis? Surely by now the fellow should know it's Sir Kingsley] But no - this is unworthy. It is surely my imagination at work, not Amis's vanity.

As we eat he reflects on Lucky Jim. 'It couldn't go wrong with that story. You know - young man meets beautiful girl, gets rid of another girl he doesn't want, goes off with the new girl, leaving behind a boss he hates.'

There certainly was a kind of universality about the story. Amis remembers with enormous glee a visiting Yugoslav professor called Miroslav Beker, who took him out to dinner at the same Bush restaurant in Swansea where he had celebrated Lucky Jim's publication in order to tell him how much the novel was relished in his country as a picture of life under Stalinism. And you can see exactly what Beker meant. Lucky Jim making faces behind the hated Professor Welch's back must have been just the sort of helpless gesture the Yugoslav professor's beleaguered countrymen were reduced to.

But was there more to Lucky Jim than the story? 'I was fortunate with my timing too. The old pre-war literary guard were still more or less in place,' Amis says. Which meant that upper-middle-class values prevailed. 'Jim Dixon was unmistakeably lower-

middle-class. It was the first time anybody had written about such a character without condescension. At least since people like Dickens. I think it was Alan Watkins (of the Independent on Sunday) who pointed that out.'

Forty years ago, there were still barricades of language, taste and class for writers to assault. When Amis wrote his second novel, That Uncertain Feeling, Victor Gollancz rang up and asked how strongly he felt about keeping in the word 'bugger'. Strongly enough to risk losing 4,000 sales to Boots Library? They settled for 'poor bloody fool', although in the novel's Welsh setting 'bugger' was actually an inoffensive term of affection while 'bloody' was a swear-word proper. There are none of these delicacies left to worry about. 'You can write about anything now,' Amis says. He is frustrated that people don't understand the change, the way his old friend Philip Larkin was written off as a foul-mouthed blimp and dirty old man when his biography was published last year being a particularly upsetting example. 'What people don't realise is that when Philip wrote 'fuck' in a letter it was an act of freedom. So was looking at pictures of naked women. Now you can write anything at all. Martin once wrote 'fuck' 62 times, I think it was, on the same page. It was his way of showing you could do what you liked.'

Amis admits to using the f- word himself now and then, though 'only after a lot of thought'. Here is where he thinks modern fiction may have lost its way. There being no barriers of class or taste left, writers are reduced to playing with language, to exactly that experimental tomfoolery he so detests. So long as he continues to write he will be sticking to fiction in plain language with understandable plots and credible characters. And if critics claim that the novel has 'moved on' since Amis's time, he will want to know where it has moved to that is any better than where it has moved from.

Hilly and he now pick at a raspberry sorbet, he and I dash down a digestif, then summon the bill and head out into the street for a taxi. The atmosphere on the way back to Primrose Hill is decidedly sleepy.

It occurs to me that, with Anthony Burgess and William Golding dead, Amis has the best claim to be regarded as Britain's Grand Old Man of letters. Though the 'old' tag may not strike quite the right note, for Amis is anything but written-out. From the moment in 1946 when he stumbled across the idea for Lucky Jim in the senior common room of Leicester University, where he had gone to see Larkin, to the date of its publication was a full eight years. But last year alone he published a book of short stories and completed a novel in October. There followed three restless days of uncertainty about what to next. Then he was off again and by now has written more than 100 pages of another novel. The Amis literary pace has only got faster.

From what he has let slip, this new novel seems to be about a literary chap of advancing years who is having his biography written by a younger journalist. Now what could have made him think of that? But Amis famously despises any writer who relies on his own life for his plots, so one can only assume that any resemblance between his fictional journalist and the one who is currently writing his biography will be entirely coincidental. Still, you never know, Amis has a good few surprises left in him yet.

Eric Jacobs's biography of Sir Kingsley Amis will be published next year

(Photograph omitted)