I don't recall much about Giovanni's: a narrow room, small tables pressed closely together, framed black-and-white photographs on the wall. Ah, but the cake! That was something special. It was so good, so rich in cream and cherries and delicate sponge, that I offered it around to everybody else in the restaurant that night, a ridiculously generous gesture by a four-year-old determined to share his good luck.

In retrospect I realise now that I was luckier than ever I knew, not simply because I had enlightened (and wealthy) parents who believed in taking small kids to restaurants, but because in 1970s London it was very easy to eat very poor Italian food. Today Britain, and particularly the capital, seems awash with Italian restaurants attempting to offer a quality product far removed from the scuffed trattorias of old: there's Latium and Paolo, Cipriani and Enoteca Turi, Assaggi, Timo and Spiga plus many more besides which we will get to in time. But back then there was precious little: Giovanni's in Goodwins Court (a favourite of Frank Sinatra when in London, who always ate the Frank Sinatra Seafood Salad), a couple of places in Soho and La Famiglia down in Chelsea. The rest was a desert.

'When I arrived in the 1970s it was mostly what I call Brit-alian food,' says Antonio Carluccio. 'A bastardised Italian food, what Italian restaurateurs thought the British wanted: avocado with prawns, a spaghetti Bolognese that was nothing like the one we eat at home.' Gennaro Contaldo, now of Passione, who arrived in 1970, is even more savage. 'The quality was zero, below zero. There was one famous place in Mayfair where I worked which insisted on making carbonara with a béchamel sauce. I complained. That is no way to make carbonara, I said. And then I was sacked.'

It wasn't that Britain was short on people who knew what real Italian food tasted like. The Festival of Britain had brought large numbers of Italians into the country to work in the catering business and a lot of them had stayed. There were some great delis in Clerkenwell, the heart of London's Italian community, and in Soho. But there was also an assumption that the British wanted a particular product from an Italian restaurant, something they felt comfortable with, and it bore no relation to the real thing. There were, in Britain, a lot of bottles of red wine in wicker baskets.

Alongside Giovanni's, one of the few rays of light was the Terrazzo in Soho, run by two Italians called Mario and Franco who would eventually become regarded as the godfathers of Britain's 1960s trattoria boom. What they served up was hardly high quality, but it did possess a certain authenticity. They also trained a lot of other restaurateurs, among them Alvaro Maccioni, who, in 1975, opened La Famiglia on the King's Road, which is still there to this day. Alvaro had the knack for getting the beautiful people into his restaurants: models, photographers, slack minor royals with a taste for gin. Before La Famiglia he'd already run a chain with his name above the door, which he'd sold to the Golden Egg group, plus a nightclub. He returned to Italy for a few years only to discover that, back there, he was now regarded as an Englishman. So three years later he flew to London and did the only thing he knew how to do: open a restaurant.

Alvaro is Tuscan and so was much of his menu, a rare breakthrough for regionality in a British Italian restaurant, which tended to regarded the country as one homogeneous whole. Occasionally, though, he did let in ingredients from elsewhere if he understood them. For example, Alvaro was one of the first people to serve sundried tomatoes. 'I knew what they were because my wife is Sicilian,' he says. 'My biggest problem was getting the customers to understand. "Sundried tomatoes?" they would say to me. "What are these old tomatoes?" My job was to educate people.'

Antonio Carluccio has been educating people for years. In 1981, Carluccio, who had been working as a wine merchant, took over the Neal Street Restaurant in London's Covent Garden from his brother-in-law Terence Conran. It is a mark of how far we have come that today Neal Street has its arch critics, people who argue it has lost its touch. In its time, Neal Street was groundbreaking: a relaxed environment serving seriously high-quality food. 'Italian food is not made to be tarted up,' Carluccio says today. 'In fact, it shouldn't be tarted up. It's about good ingredients and preparing them sympathetically and that's what we tried to do here.'

Neal Street was a seminal restaurant, not just because of the food it served but because of the people who worked there. Gennaro Contaldo worked alongside Carluccio for many years, helping to source ingredients and travelling with him across Italy for various BBC food and drink programmes. Jamie Oliver was there for a while and both Nino Sassu and Pietro Fraccari, who went on to set up the highly regarded Assaggi, put in a few years. And, of course, Rose Gray worked with Carluccio on various aspects of the business before setting up the River Café in 1987.

'We wanted the kind of restaurant where we could eat the sort of food we were used to eating in Italian homes,' Rose's partner Ruthie Rogers says. Rose Grey had lived in Italy for years and as Ruthie's husband, the architect Richard Rogers, is Italian, she had also become steeped in the country's cooking, learning dish after dish from her late mother-in-law, Dada. They were also influenced by the likes of Alice Waters and her restaurant Chez Panisse in Berkeley, California. Her emphasis on seasonality had proved that you could serve seriously good food in a relaxed environment.

The irony of the River Café - a place which sold itself on the twin ideas of home cooking in relaxed surroundings - was that it turned out to be, and remains, fearsomely expensive compared to what Britain was used to for Italian food. Ruthie is unrepentant. 'If you use the very best ingredients, that's what it costs,' she says. 'We had the best tomatoes, the best basil, the olive oil and we priced fairly.' Ruthie and Rose remain famous for the trips they make to Italy in search of ingredients. It was effort that paid off: in 1998 the River Café was awarded a Michelin star.

But the River Café was not to have the firmament to itself for long. Three years earlier, in 1995, the A to Z Restaurant group had opened Zafferano. 'We already had Aubergine and Ken Lo's Memories of China,' says Giuliano Lotto of A to Z. 'So we had a quality French and a quality Chinese. The strange thing was all three directors of the company were Italian. So now we wanted a quality Italian.' Their aim was simple: 'to have the best Italian restaurant in town'. And they were quite clear that their competition was the River Café. 'But we knew Zafferano would be different. It is,' he says pointedly, 'an Italian restaurant run by Italian people. We are brought up eating the best parmigiano, the best parma ham, and that is why Italian children are the luckiest in the world.'

Naturally, for this all Italian venture they needed an Italian chef, so they turned to a British man with a French name. 'Marco Pierre White had suggested Gordon Ramsay to us for Aubergine so we asked him now who we should get,' Lotto says. "He suggested a guy called Giorgio Locatelli, who was working at a restaurant in Victoria called Olivio.' It was a good call. Zafferano was a huge hit with the critics and, in 1999, scored its much sought-after Michelin star.

Three years later, Locatelli left to set up his own place, Locanda Locatelli, at the Churchill Intercontinental Hotel, where he soon picked up his star. To a few raised eyebrows, the kitchen at Zafferano was taken over by his long-time deputy, the less-than-Italian Andy Needham. He, too, maintained the star, but then he knows his stuff. 'I first worked with Giorgio at the Savoy,' he says, 'And he was the one who turned me on to Italian food. So after the Savoy and a stint in Paris I worked my way down south to Sardinia and up through Italy. I think you have to put in the time on the ground to really understand what the food is about.' Today, he says, London is a superb town for Italian restaurants, because of the efforts of those who have gone before. 'It's possible to source really good ingredients in the capital now, coming in direct from Italy, because of the number of quality places out there,' Needham says. 'And that's the root of it. Without the ingredients you can't make the food.'

In a story like this there are always a few diversions that don't quite fit the linear narrative. A lot of people in the business credit Alberico, the chef at Harry's Bar in London's Mayfair since 1990, with raising the level of the game for everybody. But as Harry's Bar is a members-only club, his influence has been more behind-the-scenes than direct. (He can be credited with putting one of the most expensive Italian dishes available in London on the menu; they serve a white truffle pasta when truffles are season, priced by weight. An enthusiastic truffle eater can easily splash out over £100 for that dish alone.)

The other unsung hero, perhaps because of his geographical location, is Franco Taruschio, originally at the Walnut Tree Inn at Llandewi Skirrid in Monmouthshire. Until he retired recently, Franco and his wife were there for over 35 years, reviving dishes that had been lost even in his native Italy. His vincisgrassi maceratese, a staggering lasagne of porcini mushrooms and truffles, is still spoken about in hushed tones by those who have tried it. Happily, it is still available in some of the restaurants for whom he has worked as a consultant since stepping away from the stove, including the Phoenix on the Lower Richmond Road in south-west London.

Indeed, the presence of that dish on the menu of a good but unremarkable suburban restaurant may be a sign of how far we have come. Three decades ago, when I was precociously charming the socks off the other punters at Giovanni's by handing round my birthday cake, a slice of something genuinely Italian was a precious commodity in this country. It was the poor relation to French cuisine. Now both the idea and the practice of good Italian food is widely available. We understand why good pasta costs money and we don't mind settling the bill. We may be poorer on the night, but overall we're richer for it.

·Gennaro Contaldo is creating the gala dinner at Pavarotti's UK concert.

·Jay Rayner is The Observer's restaurant critic. His new book is The Apologist.