A Cotswold farming family believe they have found the answer to sustainability by producing a crop that can serve as a food and be converted into a fuel once it has reached the end of its useful life in the kitchen. Hamish Campbell, from Cotswold Farm, near Stow-on-the-Wold, and his parents, Robert and Emily Campbell, are working together to produce R-Oil, a cold-pressed extra virgin oil made from rape seed to which nothing has been added. The first bottles were filled and distributed a couple of months ago and the findings are good. It seems the Campbell family could be on to a winner.

It all began last year when the family were beginning to despair at the falling price of wheat and rapeseed, and were wondering how they could diversify. While shopping at Tesco, Robert noticed the high price shoppers were being charged for rapeseed oil and began checking on how they could produce oil from their crop, for which they were only being offered £120 a ton.

"One thing then led to another," said Hamish, proudly displaying a bottle of R-Oil.

"We decided to go one better and use the cold-press system used to produce high-quality virgin olive oil and create a similar product from our rapeseed."

After considerable research, they found it could be done, and was, in fact, being done in other parts of the world. But there are only two other producers of cold-pressed rapeseed oil in this country - Grange Farm Organics, in Powys, and Hill Farm Oils, in Suffolk.

And so the Campbells search for a suitable press and bottling plant began.

There has been some pretty negative press about rapeseed oil in the past, particularly in the US and Canada where it's produced from a genetically modified seed. The Campbells are not using GM seeds, but have stuck to the British-grown farm standard type of oilseed rape they have always used. This is a member of the brassicaceae family - cabbages or mustards are part of it too.

Because rapeseed originally had a high erucic acid content, it was once considered unfit for human and animal consumption and only used as an industrial oil. These acids have now been bred out, however, by cross-pollination and natural methods.

The oil is obtained from the peppercorn-like seeds that develop once the plant's garish yellow flowers have died. This is the flower that has transformed the colour of swathes of our landscape in late spring from green to a startling golden yellow. If the Campbells get their R-Oil up and running they will be planting 2,000 acres of this crop next year.

It was Emily Campbell who decided on the R-Oil name, and Hamish who then spent every moment he could spare calling into the kitchens of Michelin-starred restaurants to discuss his product with the chefs. He was convinced it was worth starting at the top. "This is a quality product which I knew top chefs would appreciate once they had tried it," he said.

Hamish says R-Oil is a very versatile oil, ideal for both deep and shallow frying and for use in salad dressings, marinades, stir-fries and roasting. Unlike most vegetable oils, it is entirely unadulterated and natural, as it is pressed in the same way as extra virgin olive oil, without the addition or help of chemicals. A lot of specialist oils are hydrogenated, which means they are treated with heat and hydrogen. R-Oil is not, and therefore contains no trans fats.

R-Oil goes through minimal processing, so its goodness is not lost. It is just cold pressed before going into a series of settlement tanks, and then filtered into a 1,000-litre tank. It is bottled or canned on the farm. No solvents are used at any point of this process. The cake that remains after the pressing can be given to the beef and dairy herds, so nothing is wasted.

Because it is cold pressed, the oil has an extremely low saturated fat content - no more than 7 per cent, which is far lower than olive oil which has 14 per cent saturated fat. Sunflower oil contains ten per cent.

" It's also rich in linoleic and linolenic acid," says Hamish, "which our bodies convert into Omega 3 and Omega 6, both of which are good for one's health as they reduce the risk of heart problems and help lower high blood pressure." The oil tastes good too. Hamish describes it has having a delicate sort of nutty flavour.

Obviously R-Oil hasn't got the distinctive peppery taste of olive oil - nothing could ever quite match that. But it tastes fine and is jolly useful when creating a dressing or sauce which requires an oil that doesn't dominate the final flavour. It is good for frying too, and produces a very crispy product, but is best if kept at 180C or below.

Robert Campbell describes R-Oil as a purely natural product which, when used sensibly, does everything asked of it. Once it has passed its useful life in a commercial kitchen, Robert will arrange for its collection so that it can be converted into biodiesel, which the family use to run their vans.

Janet Thorn, senior lecturer in nutrition, at Oxford Brookes University, who believes that all oils should be used in moderation, says that in many ways R-Oil could be even better than olive oil. She is particularly impressed with its low saturated fat content and the fact it doesn't travel halfway round the world to get to our plate. "It's always good to discover a quality produce of high nutritional value that's being produced on our doorstep and delivered in vans running on fuel created from the same product once its kitchen-life is over."

R-Oil is on sale, at around £4 a litre, at Gluttons, in Walton Street, Oxford and Cornucopia, in High Street, Eynsham. For further information about R-Oil go to www.r-oil.co.uk