Luton Hoo, treasure house of a diamond dynasty, is up for sale for pounds 25m

The old order is changing for ever in Bedfordshire. Luton Hoo, one of England's grandest stately homes, has been put on the market for pounds 25m.

The sale, which will be one of the most significant private property deals in 50 years, marks the final episode in the sad story of the Phillips family, who inherited the Grade I listed mansion in 1977.

The 1,545-acre estate, which includes a spectacular park designed by Capability Brown, a 50-acre lake, a pheasant shoot and an Italian garden, has for a century been home to the Wernher art collection.

Since the suicide of Nicholas Phillips six years ago, his widow Lucy, an Austrian countess, together with his executors, has been struggling to reduce the pounds 23m business debts he left, resorting to the sale of family art treasures and to the leasing out of the house as a rock festival venue and a film location.

Luton Hoo will be familiar to many as one of the houses featured in the film Four Weddings and a Funeral. It also took the part of Manderley in the recent television version of Daphne du Maurier's Rebecca.

News of the sale comes as a surprise in the light of the unexpected success of some of the countess's money-raising ventures. One painting, a small Winter Landscape of 1650 by the Dutch artist Aert van der Neer, went at auction for pounds 2.3m last year. It had been thought it would raise only pounds 700,000.

But the biggest asset put up for sale from the collection was a 15th- century Spanish painting by Bartolomeo Bermejo, St Michael Triumphant Over the Devil. It went to the National Gallery for pounds 10m, with the help of the National Heritage Memorial Fund.

The mansion itself was built for the 3rd Earl of Bute, the Prime Minister to George III, and its exterior remains largely unchanged. The interior was extensively remodelled by the architects who designed the London Ritz when the estate was sold to Sir Julius Wernher at the turn of the century.

Sir Julius had amassed a fortune in the South African diamond mines and was at that time one of the richest men in the world.

When he settled in England he started to build up a collection of Gothic and Renaissance works of art which were passed on, as the Luton Hoo Collection, to his second son, Major General Sir Harold Wernher.

Sir Harold's wife, Lady Zia, was a cousin of Nicholas II, the last Tsar of Russia, and brought with her a remarkable collection of Russian art, including the work of the Imperial court jeweller Faberge, which did much to define the character of Luton Hoo this century.

What remains of the collection is owned by a charitable foundation formed by the late Mr Phillips and his cousins. Administrators of the foundation plan to rehouse the collection after the sale, ensuring that it remains on public display.