Had farmers tending British watercress beds at the turn of the 19th century declared a National Watercress Week, the picturesque village of Ewelme, where watercress once grew in profusion, would have been celebrating this event in style.

Sadly, the historic watercress beds of Ewelme, which flourished for centuries thanks to the crystal clear Chilton spring water that runs through Ewelme Brook in which it grew, no longer produce watercress commercially. Cries of "Fresh Ewelme cress" were once a familiar sound in Covent Garden and this salad leaf was a favourite of kings. Now we can look at, but not buy, the annual harvest that Ewelme Brook yields.

The beds were closed down in the 1980s. They are now being lovingly restored thanks to the vision and energies of members of the Chilton Society and local enthusiasts such as Beryl Hunt who masterminded a fight to retain the beds. But watercress is still not being harvested commercially at Ewelme.

So when we celebrate National Watercress Week which begins today, it's the British growers based mainly in Hampshire and Dorset who will be promoting their produce this week as members of the Watercress Alliance.

Watercress (Rorippa nasturtium aquaticum), is probably best known as a classic ingredient for soup, but as its distinctive mustardy flavour is said to have health-giving properties and can help enrich many other dishes, it's worth taking this promotion seriously.

The valuable properties of watercress have been known for centuries. In Henry VIII's time it was reputed to possess curative and aphrodisiac qualities. This is why the king, who claimed Ewelme Manor as a royal residence, is believe to have bathed daily in what is now called the King's Pool, in hope that his ulcerated legs would benefit from the healing power of the water.

Ewelme watercress was also reputed to have an amazing effect on infertile wives, which lead to the local saying "there's a baby in every bunch".

But it is not only the British who take this vegetable seriously. The Chinese, who have been eating watercress for centuries, prize it for its tonic qualities and use it to cleanse toxins from the body. The ancient Greek General Xenophon made his soldiers eat it as a tonic, and the Romans and Anglo-Saxons used it to fight baldness. The Irish also believed in its virtues, describing it in early manuscripts as a pure food for sages. Today's scientists get excited about it for other reasons, having discovered the anti-cancer potential of the compound responsible for giving watercress its distinctive peppery flavour. Watercress is a member of the cruciferous-vegetable family which includes broccoli, cabbage, cauliflower, kale, turnip, Swiss chard et al. These are all considered an excellent source of a family of anti-cancer phytochemicals called isothiocyanates. But what makes watercress stand out from the other crucifers is that it contains high concentrations of the compound phenethyl isothiocyanate, or PEITC, which is thought to reduce our susceptibility to certain cancers. It is also thought to neutralise the key tobacco carcinogen and zap cancer certain cells by inducing them to self-destruct. Apparently, clinical trials on humans to test the efficacy of watercress are already under way and offering some very positive results.

But that's not all it offers. Gram for gram, watercress contains as much Vitamin C as oranges, more calcium than milk and more iron than spinach. It's literally bursting with beta carotene and Vitamin A equivalents, which are great for healthy skin and eyes, and it's a good source of folic acid. It also contains antioxidants which can help to mop up potentially harmful fee radicals and compounds known as glucosinolates. The antioxidants are responsible for its peppery flavour.

Then there is its remarkable taste -- watercress enthusiasts don't have to be told of its many culinary attributes. They know only too well that beside being packed with vitamins, freshly picked watercress radiates a freshness and vitality that can turn a salad into a gastronomic feast. Try serving it tossed in freshly squeezed orange juice and olive oil and mixed with slices of orange and a soft cheese, or throwing it into a stir-fry at the last moment and allowing it to wilt but not cook right through -- it's delicious.

Perhaps one of the most satisfying ways of using watercress is to pack it into a sandwich with egg or cheese to obtain a fiery, peppery, health-giving crunch with every bite. It can also be chopped and scattered on a dish of creamy scrambled egg to great effect.

Watercress is also considered a classic garnish for game because of its vibrant colour and attractive leaf formation. Steak houses such as Berni Inns, which flourished in the 1970s, adopted this Victorian idea and served it as their standard garnish with steak and chips for years. Indeed, it's still considered the ideal garnish for meats, fish or cheese.

To celebrate National Watercress Week, The Oxford Times is teaming up with Geest, one of the UK's major watercress producers, to launch a search for the region's most delicious watercress recipes.

They are convinced that Oxfordshire's links with Ewelme's ancient watercress beds could mean that there are countless recipes still being used in our area that have been passed down through the generations.

They are offering kitchen-ware shopping vouchers worth a total of £500 for the most mouthwatering recipes, which will be judged by a team of chefs at the Geest Culinary Academy in Peterborough. It doesn't have to be a family recipe, you can also send a recipe that you have developed yourself or customised from a restaurant meal.

All you have to do is write out your recipe and send it, along with your name, address and telephone number to: Watercress Recipe Competition, Promotions Department, The Oxford Times, Newspaper House, Osney Mead, Oxford OX2 0EJ. Closing date for entries is Friday, June 6.