I am to meet the legendary food critic Fay Maschler with her husband, thriller writer Reg Gadney, at a restaurant called As Greek as it Gets. The table is booked under the pseudonym 'Fox'. 'It's just opened,' she tells me over the phone. 'I don't know what it will be like.' She's chosen it because the couple have a holiday home in Greece where they feast on the local produce but it swiftly transpires that this new venture in west London is sadly lacklustre. An irritating punning menu flags up 'Favoureats' and 'Up-Etizers', there is loud muzak and video screens, and the decor is a wearing shade of burnt orange. She probably wouldn't give a fig about any of this if the food was delicious but we are served some of the dreariest Greek cuisine this side of the Peloponnese. Going somewhere else is mooted but by the time the barely touched dishes (all served with fries and pitta) are taken away we've forgotten dinner and consoled ourselves with ouzo.

'You didn't like the food?' asks the waitress. 'It was too much,' says Fay politely, signing the bill.

Oddly, this turns out to be the owner's lucky day. Fay is known as much for her damning critiques as her rave compliments, but she decides that As Bad as it Gets - as she takes to calling it - is so disappointing it isn't worthy of writing up. 'But,' she says cheerily, 'at least you can say that Fay Maschler will go anywhere.'

It's true. In 33 years as the London Evening Standard's restaurant critic, she has gone pretty much anywhere in search of a decent bite to eat. When she started out chicken kiev was sophisticated. Now bacon ice cream and snail porridge are the talk of the town. Eating out at least five nights a week, she has seen trends come and go: peasant Italian, posh Irish, fish heads, pigs' trotters, white bread, blackened cod, raw beef, triple-cooked chips. Over three decades Fay has scanned the menu in almost 7,000 restaurants. By anyone's reckoning, that's a lot of hot dinners.

This softly spoken woman, barely over five feet tall, can make grown men quake. Talk to chefs about her and they're quick to bandy words like 'doyenne', 'queen', and 'grande dame'. True, although she's known for her integrity, they also understand which side their bread rolls are buttered. It doesn't do to mess with Maschler. Jamie Oliver: 'In the last 30 years she's been a key figure in helping British chefs up their game on an international level.' Gary Rhodes: 'Her reviews are like a signal that you are still worthy and fingers crossed you'll get a good one.' Antony Worrall Thompson says she's been his unofficial, unpaid career consultant. According to Gordon Ramsay - who once had the misfortune to fall out with her, but more of this later - a glowing review in her Wednesday column is better for business than a Michelin star.

Journalists aren't known for complimenting their own but there's no shortage of praise from other restaurant critics either. The Observer's Jay Rayner: 'She has real power.' Giles Coren of the Times magazine: 'People want informed, balanced reviews. That's what they get from Fay. The rest of us are a bunch of know-nothing twits.'

Since winning a competition for a three-month contract to write the newspaper's restaurant reviews in 1972, she has survived eight editors and written more than two million words. She says she's sure a couple of bosses have thought about getting rid of her over the years 'for someone younger and more interested in who is at the next table'. But they would surely ditch her at their peril. Readers and those in the restaurant business follow the column because they trust her. As Coren says: 'She puts bums on seats more than any of us. If she says an Indian is the fourth best one in Southwark - then it is.'

I ask the Michelin-starred Italian chef Giorgio Locatelli whether her power is really such that she has influenced a dish: 'If she didn't like something,' he says 'I would go back to it and look at it again. Maybe I would change it, maybe I wouldn't. But I would definitely have another look at it.' He remembers her giving his first London venture, a restaurant called Olivio, a poor review. 'It hurt. But she was absolutely right. Chefs think too much that they're the only ones who know what people want. It might be difficult to admit but she knows, too.'

He estimates that a good review from Fay will increase his week's covers by 40 per cent. She agrees: 'I can fill a restaurant. Particularly if I discover one that is reasonably priced and good. Whether it stays full depends on whether they are consistent.' Has she ever closed one? 'I hope I haven't. They tend to do that all by themselves.' I recall friends of mine who opened a restaurant in the City, received an appalling Maschler write-up and did the only thing they knew how - they framed it. Twelve months later they'd shut down.

One of the first restaurant meals

Maschler remembers was a buffet in Greenwich, Connecticut, piled high with roast potatoes, corn on the cob and spare ribs. She was 12 and the notion that she could eat anything she wanted was fabulous. She was born in India but her family - she has a sister, Beth Coventry, who is a chef - had moved to America via Surrey. Once she became a restaurant critic, her mother liked to recall how, as a child, her daughter would spend an age dissecting the menu. 'My mother was a very good cook, even when you couldn't get any decent ingredients. We would have salad with oil and vinegar dressing which would have been unheard of then.' Meanwhile her father, who for an unpopular period forced the family to be vegetarian after consulting a famous naturopath, grew the family's greens in the garden.When she was sent to a convent boarding school Beth said her sister 'turned into a skeleton' by refusing to eat the awful meals. 'What annoyed me was that if they could cook good food on feast days why couldn't they do it all the time?' During lonely summers in Connecticut she lived in the kitchen. 'I discovered I could cook and that I enjoyed it. I'd do difficult things like puff pastry or meringues. I liked the idea of something dramatic happening in the oven. It was also a way of winning approval from my parents.'

Her father didn't agree with the idea of young women going to university so after her A-levels Fay reluctantly worked as a secretary and then as a sub-editor on the Radio Times and occasionally as a model. This was the Sixties. She shared a flat in Chelsea with a Rolling Stone journalist and was going out so often she says she barely slept. However she still managed to celebrate her 21st by serving dinner guests individual poussins from Smithfield Market.

Her talent for cooking goes some way to explain why she's held in such high regard. She understands food, knows when ingredients are at their best. Jay Rayner once committed the grave error of serving her unripe peaches in Muscat wine for pud: 'The chef Bruce Poole was at the meal too but I was much more nervous about Fay. Afterwards I admitted it had been a bad idea to do the peaches. She retorted: "So why did you?"'

In 1969 she was working as an advertising copywriter when she met Tom Maschler at a party held by Richard Neville of the infamous Oz magazine. Maschler was the buccaneering young publisher who revitalised Jonathan Cape. Fay was 24 and pregnant with their first daughter, Hannah, when they married (Tom's chum Arnold Wesker was best man). The couple, who were to become a fixture of the Seventies literary crowd, were together for 12 years, yet she is barely mentioned in his memoirs.

Tom was 'famously mean so we'd never go out to eat' she says, looking back. But at least life married to a celebrity publisher offered the chance to practise her cooking on his authors. The only problem was that the likes of Jonathan Miller, Kenneth Tynan and Frederick Raphael would pitch up all wanting to show off and inevitably the evening would end up in an argument.

It was Arnold Wesker's wife Dusty who spotted the Evening Standard competition for a restaurant critic. Maschler applied under her maiden name. 'I'd always been good at winning things. And anyway, it was a bit like copywriting.' As it turned out the shortlist was fiercely debated until the editor Charles Wintour threw up his hands and said 'Fuck it! Give it to the woman!'

At the time there was very little media interest in food. 'None of the nationals had permanent restaurant critics,' recalls food writer and TV presenter Jonathan Meades. 'They still hadn't when I started reviewing for the Times in 1986.' Her boss told her she'd soon grow sick of the job but she took to championing ethnic places which is still a specialism today. In the mid-

Eighties, restaurants like Kensington Place, Bibendum, the River Cafe and Alastair Little opened within 18 months. Suddenly, fat-cat Londoners had somewhere to eat out and the money to spend there. Maschler recalls: 'I remember Alastair Little being plugged on the front of Elle and thinking something exciting was happening.'

The second time we meet, it's lunch at a gastropub near Fleet Street. When she suggests I order first, I suspect that eating out with Fay Maschler could be like going to Harvey Nichols with Trinny and Susannah. Although less grand in person than her reputation suggests, I imagine she can be withering when she chooses to be.

I plump for a safe option of asparagus followed by lamb. Maschler orders duck hearts and I realise I've done the fashion equivalent of choosing a beige V-neck sweater. Could she order for me? Looking momentarily astonished, she suggests the confit of new season garlic with goat's cheese to start, followed by salted ox tongue - a dish I have assiduously avoided since school dinners. She orders a soothing sounding risotto primavera which she tells me is an excellent way to discover how good the chef really is. She always books under a false name and although she's often recognised ('I'm betrayed by the waiters') she's only once tried a disguise, at Marco Pierre White's Harvey's. 'I wore an itchy auburn wig - I looked like Alma Cogan. He came out of the kitchens and exclaimed: "But Fay you have cut your hair! So have I!"' Now she relies on shuffling into a restaurant behind six-foot-tall Reg. 'Restaurant managers tend to only ever make eye contact with the man.'

After lunch she inquires after my starter. I quickly realise how difficult it is to actually describe food. Sometimes it's a struggle, she agrees. 'It's easier to write up something that is revolting.' Although she's not a natural fan of the likes of AA Gill or Giles Coren, who tend to play for laughs, she can also be the put-down princess when she chooses to be. She has likened pea soup to 'frozen Pepsodent', soufflé to 'an old bath sponge', a doomed carrot cannelloni to 'a vegetable-filled condom'. On a memorable occasion she debated 'how best to convey a piece of food that is in your mouth back to the plate'.

While Locatelli compares her to the Queen, Gordon Ramsay's nickname for her is Maggie Thatcher. He reels from the time she said one of his kidney dishes was like 'toxic scum on a stagnant pool'. This was six years ago and he's still having nightmares about it. 'It was like someone kicking me in the bollocks with a pair of size 14s.' When he lashed out and complained, they fell out. 'Looking back I realise I was 29 and immature. I overreacted and I've apologised since. But she ignored me for five years. I've paid the price of falling out with her,' says Ramsay. Maschler tells me that recently he wrote saying she was the only restaurant critic he planned to invite to his new launch. 'Mind you, I'm sure when I get there the first person I'll see will be Giles Coren,' she says drily. 'But we are friends now... I like his wife.'

Ramsay's isn't the only ego she's deep-fried. She said a meal of Jamie Oliver's at Monte's was 'gauche' and 'joyless'. 'He'd gone from being golden boy at the River Cafe to being the Naked Chef and I don't think he'd been criticised before. A mutual friend told me he was really upset.' She's since become a patron of his Fifteen Foundation. She's called Terence Conran a shopkeeper restaurateur. Richard Shepherd who owns the Langan's chain has banned her for 15 years. She says it's no hardship: 'He's one of those men in the restaurant business who couldn't stand the idea of being criticised by a woman.' And anyway, she and Reg did recently nip into Langan's Bistro. 'We were nearby and we wanted to eat out.' What happened? 'No one knew us from a bar of soap. We had an indifferent meal and left.'

She's been threatened with several law suits but the only time there was a pay-out was when she compared a dish to minced mouse. 'Apparently you can't say that unless you have knowingly eaten minced mouse.' Which as far as she's aware she hasn't - although she did go through a period of having food poisoning all the time. 'I used to have to stop the car to throw up on the way home. But I think I've built up my antibodies now so I'm never sick.'

What she hates are expensive, pretentious restaurants where she keeps being asked whether she's enjoying herself. 'I like talking to the person I am with. I hate it when I choose and the waiter repeats it all back, then when the food comes, repeats it again. I think: "For God's sake, just let me get on with my meal!" I know what I've chosen, I don't need to be told. I suppose some people might want to be waited on. But I like it when they leave the wine on the table and let us get on with it.' She also hates deskbats (front-of-house people that look at you as though you're usually to be found at KFC) and piped music (although occasionally, if it's a song she knows, it's OK).

She does, however, have some of her own critics. Insiders whisper that she goes to too many 'soft openings' in a bid to be first with her review (it's usually a race between Maschler and Jan Moir of the Telegraph). She says wanting to be first is part of being a journalist. Worrall Thompson recalls her turning up unexpectedly when he'd just taken over a restaurant called Dan's. 'I said "That's a bit mean," and she said, "Well, you're already charging full prices."' Since then he's offered cut-price menus in launch weeks in the same way that theatres charge less for previews.

Most people I speak to are astonished by how long she's done the job. Eating out every night can end up being a bit of a slog. Genial Reg, a lamb or steak man, says he needs only to look at food to put on a stone. She does her best to avoid the bread basket and dessert. Drinking too much wine is a worry but every so often they give up for a while. On a rare night at home she says she's never knowingly eaten a TV dinner: she'd rather eat a boiled egg.

She says the job has suited the way her life has changed over the years. When she was a young mother she saw her three children during the day, leaving her evenings free. After her divorce it was a wonderful way to date men. When she met Reg he loved the idea of eating out all the time. 'I'm still enthusiastic about it. It's a profession based on nurturing and feeding, so many chefs are, in fact, very nice.'

Her current contract will end in 2007 when she's 62. She's not sure what will happen then, though she has been approached to write a memoir. As her new best friend Gordon Ramsay says: 'The saddest day will be when Maggie Thatcher decides to stop.'

She said that?

'The put-down princess' Fay Maschler in her own words ...

'The first threat of a lawsuit I received came from a restaurant proprietor who didn't seem to realise that the rules can change. He was outraged that the pastiche French food he had bullied his customers into believing was the real thing could be criticised. And by a woman. The world of chefs and restaurateurs is a male-dominated place, a sort of minor public school where the ability to browbeat counts for a lot.

Years ago, Marco Pierre White said that I gave him a bad review because he wouldn't sleep with me - a calumny that's tricky to deny without digging yourself in deeper - and Gordon Ramsay and I have only in the past few years put behind us my description of the sauce for his dish of kidneys as looking like 'toxic scum on a stagnant pool'. Luke Johnson [ex-owner of the Ivy, J Sheekey and Le Caprice] asks what moral right does a restaurant critic have to make judgments. I say: 'What moral right do some restaurateurs have to trade unchecked while inflicting on the public overpriced mediocre food unprofessionally served?'
November 2004

'Antony Worrall Thompson is co-owner of the new Kew Grill. I've recently read his rollicking autobiography where the account of his formative years explains a lot about the driven Woz. I can't remember if one of his school reports said "Tends to bite off more than he can chew," but, if not, I'll say it instead.'
March 2004

'"Good afternoon," said the waitress as we sat down in the restaurant at 9pm. She gazed at the absence of light coming through the string-like curtains on the exterior wall like an anxious dormouse who's been too long in hibernation.'
May 2005