FOOD & DRINK / Sauce on everyone's lips: Pesto was around before the Romans; in just three years it has swept through Britain. Michael Bateman charts the phenomenal rise of a north Italian conqueror

COMING SOON, to a restaurant or supermarket near you, Pestomania. England's green and pleasant land is on the verge of being swamped by the savoury Italian sauce, pesto. It is popping up everywhere; though there aren't pesto-flavoured crisps on sale yet, nor pesto sandwiches in M & S, nor pesto hot drinks or pesto shampoos. But it's only a matter of time.

Pesto is the pungent, cheesy, garlicky, nutty sauce, with the perfume of freshly picked basil, which is the favourite seasoning for pasta and soups in the region around Genoa in northern Italy. But now pesto is conquering corners of these islands that not even the Roman legions managed to reach. In urban Belfast and in the deepest valleys of Wales, pesto is the sauce on everybody's lips. On Speyside, Baxters, soupmakers to the Queen Mother, see fit to add a soupcon to their vegetable soup to make the Provencal soupe au pistou.

It is indeed an unfashionable restaurant these days which doesn't do variations on a theme of pesto, blobbing the sauce on any food except the obvious ones, soup or pasta. On fish, on chicken, on baked potatoes. In fashionable Sloaneravia, at the Michelin- starred Bibendum, pesto is the key to one of chef Simon Hopkinson's signature dishes, baked aubergine.

Every supermarket stocks pesto now. Green pesto and also red pesto. Sainsbury's sells 'Classic Red Pesto', which will come as a surprise to Italians. They have never heard of red pesto, let alone tasted it. So red pesto is 'classic' in the sense of classic as in Classic FM - in other words not classic at all.

Red pesto contains sun-dried tomatoes (thus we cheerfully mix the sauce of north Italy with seasoning of south Italy and cunningly combine the two most fashionable foods), but the next pesto on the way from Sacla, the leading Italian pesto exporter, is a white one, that's pesto with cream in it, which is an even greater anomaly. The Italian chairman of Sacla, Carlo Ercole, went white when the idea was suggested: 'Creamy pesto,' he exclaimed, 'It should be called criminal pesto.' So it can only be a small step to pesto with black olives, with green olives, with anchovies, with capers, with green peppers, red peppers, chillies. And then, who knows?

It is a curious phenomenon that a sauce which has been around since Roman times should take off like this. Why? In the industry people point to the pasta revolution. In three years pasta sauces have soared to sales of pounds 65m a year; tomato and meat, at first, but now pesto has come up on the outside rails, last November taking eight per cent of the market.

To trace the socio-gastronomic history of this phenomenon we need only look back to 1990, when Sacla launched its full-scale assault on the British market. (Its sauces had been imported before, but were only available in specialist shops.) Its product was as different from home-made pesto as real chicken stock is from a stock cube, but it provoked interest, especially when it was promoted with energetic public relations and advertising. 'You know when you are getting through to people,' says Conal Walsh, the PR man who handled the launch, 'when the Newcastle Journal praises the product and then observes that although it's OK it doesn't really compare with the real thing, and proceeds to tell its half million readers how to make their own, using dawn-gathered basil, freshly roasted pine nuts, hard pecorino cheese and estate-bottled extra virgin olive oil.'

Conal Walsh's cuttings book is a record of pesto on the campaign trail: Hey Pesto] the headlines yelled. He scored notable successes at the stump from the Chertsey and Addlestone Herald to the Daily Mirror (in an A to Z of edible Christmas gifts); from Today ('a super buy for the summer') to the Rugby Preview ('ideal for risottos, stuffed peppers, omelettes and baked potatoes').

In the dailies and the Sundays, in the weeklies and the freebies, writers took turns to salute pesto. 'Pesto is the finest of all sauces for pasta,' observed Nigel Slater. 'It may be sacrilege, but I spread it on toast.' (Not sacrilege, the only sacrilege is to ignore it.) Combine it with pork as a stuffing for triangles of homemade pasta, said Josceline Dimbleby in the early days. Stuff potato balls with it, she said boldly last month.

By 1991 Sainsbury's had introduced its 'own brand' pesto (pasteurised to give a long shelf- life) and followed it up with a fresh one to sell from the chill cabinet. Safeway and Waitrose will be stocking a new higher-priced 'gourmet' pesto this month. It is produced by Chalice, an Anglo-Cypriot company noted for its kalamata olives, which went to Italy to get the real thing. 'We looked at 60 or 70 brands before we chose our manufacturer,' says the company director Anna Achilleos.

It worried Mrs Achilleos that the pesto kept slipping off the pasta. Then she discovered that in Genoa pasta and pesto were often eaten with a boiled potato to mop up the sauce. 'We've put some natural potato powder in our sauce, and it helps the pesto adhere to pasta.'

The longest-running contender in the British pesto market is actually a Welsh company, Zest Foods. Managing director Tim Clarke started making and bottling the sauce in his garden shed in 1985 and now he's selling pesto dressings and pesto dips right across the board from Fortnum and Mason to Tesco, from Virgin Atlantic to Cathay Pacific.

Perhaps he wasn't in exactly the right place when he started, but he did pick the right time. The same year he set up in his shed, Sally Clarke opened Clarke's in Notting Hill Gate, introducing pesto along with other ideas such as balsamic vinegar, rocket and sun-dried tomatoes from California, where there had been a renaissance in Italian food. Then in 1987 Ruth Rogers and Rosie Grey opened The River Cafe in Hammersmith. They went all the way, creating their own Italian Renaissance in London. New Wave cooks such as Alistair Little, Simon Hopkinson and Antony Worrall Thompson were soon up to their elbows in pesto.

Pesto wasn't unknown to earlier cookery writers. In 1954 Elizabeth David wrote about pesto repeatedly in her classic book on Italy, proclaiming it to be the best sauce for pasta. Perhaps, but in Britain in the early Fifties you couldn't buy any of the ingredients to make it.

Nor did we jump to it when Robert Carrier wrote The Great Dishes of the World in 1963 and praised pesto both in its Genovese and Provencal forms. 'I encountered it when I lived in St Tropez, in soupe au pistou. I didn't know there was any other kind. I had ambitions to be a singer and was travelling Italy with a company doing Oklahoma, when we came to Genoa, and that's when I discovered Genovese pesto.'

Robert Carrier assumed that it was the Romans who had taken it to Provence, but when he came to write his most recent book on Provencal cookery, his research revealed that the basil-flavoured pesto predated the Romans by some centuries, and summer basil preserved in oil was the invention of the native Ligurians, whose territories extended from beyond Nice in France to La Spezia in Italy.

It is the heady scent of the herb sweet basil, picked while the sun still shines on it, preserved in the best olive oil, which is the glowing green heart of a Genovese or Provencal pesto. Pesto in itself means no more than 'pounded'. All over Italy (and even in Spain, where the Catalan picada is a pesto) there are mixtures of pounded herbs and nuts. In the south of Italy walnuts take the place of the pine nut of the north, and sometimes flat-leafed parsley replaces basil.

With so many inventive uses offered for pesto at home, is there anything left for the restaurant chef to explore? If they are not doing unusual things with their pesto, chefs are putting their own spin on it, substituting parsley or coriander or mint for basil, or other nuts, walnuts, cashews or hazelnuts, for pine nuts.

Paul Rankin, owner-chef of the Michelin- starred Roscoff in Belfast, first tasted pesto in California and thus has a relaxed attitude to so-called authenticity, experimenting by changing ingredients. He leaves out the cheese for a sauce for fish. He adds sun-dried tomatoes to it to make a vinaigrette dressing for salads. 'The name pesto helps sell any dish. With so many people eating more pasta, they want something to give them a good kick in the pants. Pesto does that.'

BUYING PESTO

The freshly made pesto in cartons from the chill cabinets is better than the pesto in jars, which has been pasteurised to increase shelf- life; this short period of 'cooking' affects flavour. Commercial pesto often has the stringy, stalky bits of the herb that you would discard if you were making it at home. But don't even think about using dried basil; it tastes like hay.

SALLY CLARKE'S HOME-MADE PESTO

Serves 4 to 6 as a pasta sauce

2 bunches basil leaves, torn from their stalks

4 small cloves garlic

4oz pine nuts

1/2 pint/300ml extra virgin olive oil

2oz grated Reggiano parmesan

1/2 teaspoon sea salt

freshly ground black pepper

With the blade of a broad knife crush the garlic and the salt to a cream.

Fry the pine nuts in the oil to colour them lightly. Reserve the oil. Let the pine nuts cool, then chop finely, but not to a paste.

In a blender with sharp blades, or with a sharp knife (to avoid bruising the leaves which would then turn an unappetising brown) chop the basil quite finely but not to pulp. Blend with the oil briefly.

Blend with nuts, equally briefly. Stir in the parmesan, but avoid using a blender so that the graininess of the cheese is preserved. Season with pepper. Add more oil, if you like your pesto runnier.

Serve cold, stirred on to hot pasta, or into vegetable soup. Keep what you don't use in in a jar in the fridge, covered with a film of oil.

For a punchier pesto use pecorino cheese if you can get it.