After a worldwide search for a food staple to feed the baby boomer generation, scientists struck gold in a field in Marlow, Buckinghamshire.

The tiny organism they found was used to produce a fungus, and two decades and a few refinements later the first batches of Quorn emerged from the production line.

Yesterday the appeal of the protein-rich meat replacement was underlined when Premier Foods attributed a doubling of its profits to its rising popularity.

Profits at Premier, the owner of Angel Delight and Branston Pickles, rose in the past six months to £27.9m - a year-on-year rise of 123 per cent - thanks largely to the vegetarian line. One in five households now regularly buys Quorn.

The Quorn range, which was launched with a humble vegetable pie, has since been extended, and Premier, which bought the brand for £172m last year, has added products such as fajita strips and satay sticks, and invested heavily in marketing.

However, the surge in Quorn's popularity appears to have less to do with its reliable vegetarian customer base, and more to do with its low-fat properties. On top of an estimated three million vegetarians, Quorn has a growing number of calorie-counting devotees. Premier said the proportion of households regularly buying Quorn had risen to 19.3 per cent from 17.7 per cent a year ago.

"One of its biggest attractions, especially among female customers, is that it is low in fat," said Collette Walsh of the Vegetarian Society, which endorses Quorn. She said that as a meat substitute it had no rivals, pointing out that the Linda McCartney range had soya as its base, not fungus.

"It has been particularly popular among vegetarians when they first choose to give up meat because of its convenience. Quorn provides a good variety of products such as sausages burgers and mince."

Quorn is a leading brand of mycoprotein food product sold as a meat substitute, but is not suitable for vegans since it contains products derived from eggs.

It is grown from soil mould, dried and mixed with egg which acts as a binder. It is then textured, giving it some of the character of meat. Quorn is high in vegetable protein and dietary fibre and is low in saturated fat and salt.

Although the food shortage forecast for the Eighties did not materialise, Quorn became a hit - albeit slowly - with consumers. It sold well in the canteen at the research centre where it was developed, but it was not until 1994 that it entered the mainstream, hitting the shelves at Sainsbury's.

By the end of the Eighties Quorn was popular with vegetarians and those who had cut down meat. Manufacturers phased out the use of battery eggs in Quorn after objections on ethical grounds from vegetarians.

As well as cubes and minced Quorn, available in Europe and the United States, it comes in a variety of forms such as pizza, lasagne, sliced "meat" and even the "McQuorn" burger, introduced in McDonald's to the approval of the Vegetarian Society.