Well known for his love of organic farming, the Prince of Wales has stepped in to help save a farm from developers.

The prince has donated a tour of his own organic farm at Highgrove in Gloucester-shire to a charity auction to help raise money to stop Fordhall Farm in Shropshire slipping from the family who have farmed it for centuries.

The farm, near Market Drayton, is being run by Ben Hollins, aged 21, and his sister Charlotte, 23, after their father Arthur died last year.

As tenant farmers their family has worked the fields since the 1700s, but they have now been told the landlord wants to sell. They must raise £800,000 if they want to buy the farm, otherwise it will go up for sale in July.

They are fighting back with a scheme thought to be the first of its kind in England - issuing thousands of "cooperative'' shares, each costing £50. They cannot be traded and no profits can be made from them. The family hope a trust will hold the land for the community so it can never be developed.

Prince Charles's donation will be auctioned off at a charity ball for the farm at Harper Adams College, Shropshire, on May 14.

Many keen supporters have stepped in to help the family, with £80,000 already raised.

Even Sting has expressed an interest, reportedly donating £2,000.

Miss Hollins said: "It was really exciting to hear such a fabulous prize had been donated. There is a three-year waiting list for a tour so it is an incredibly generous offer and a symbol of how highly Prince Charles regards the campaign. We wrote to the Prince and he wrote back wishing us luck. So we asked if he would like to donate a prize and he did."

* Tickets for the ball are £50. See the Fordhall Farm website at www.fordhallfarm.com