Another British collection, another foreign buyer. The private papers of British author Christopher Isherwood have been sold to a Los Angeles library for a vast sum, the latest in an apparently never-ending stream of treasures sold abroad.

In one year, to June 1998, prized works and art totalling �18.9m went to foreign buyers.

Sometimes, it seems the leeching outwards of national works of art and valuables is unstoppable. From the outcries that ensue, one might conclude that nothing is ever done to stem the flow.

Those working to keep valuables in the UK face two major hurdles: the phenomenal price tags involved and cash pressures on museums and galleries hoping to make bids.

Lost to the nation

UK institutions struggle to compete on the international marketplace. The Isherwood collection, which included diaries, literary drafts, unpublished poems, and annotated books, is understood to have fetched several million dollars.

The Huntington Library won a bidding war against four other major US institutions. It appears that no British institution had a chance to bid and the British Library said it would not have been able to compete on price.

Van Gogh's Sunflowers went under the hammer to a Japanese buyer

The most famous British auctionroom dismay came with the sale of Van Gogh's Sunflowers, for which the Japanese Yasuda Fire Insurance Company paid �24m in 1987 - the highest price ever paid in London.

A fine Poussin landscape was allowed to leave Britain 18 months ago after no institution was found prepared to pay the �15m cost. Temps Calme was sold to the Getty Museum in LA by the trustees of Sudeley Castle in Gloucestershire.

Then last year, the painting Van Tromp by Turner, said to be the forerunner of impressionism, was lost to the nation when it was sold to the Getty organisation in the US.

Six months later, art lovers were outraged at a reported government deal allowing an important private collection of Pre-Raphaelite works - worth up to �60m - to go to America.

Galleries' deadline

But the government is not insensitive to demands for efforts to keep masterpieces in the UK.

Only two months ago, ministers imposed an export ban on a late Rembrandt, Portrait of an Elderly Man, which had been sold to a Dutch buyer for more than �9m. It is one of only three authenticated late male portraits by Rembrandt in Britain.

British galleries and institutions were given three months to come up with the cash. As the deadline looms, the art world holds its breath.

The Three Graces were saved at the eleventh hour

And last July, the government wrote off about �8m in tax owed by the late Duke of Northumberland to save for the nation the Sherborne Missal, the greatest English illuminated manuscript of the late Middle Ages. It was feared it would have been sold abroad for �15m or more.

The lack of any coherent system for saving heritage pieces was most notably highlighted by the row over Canova's famous The Three Graces. The 19th-century marble sculpture nearly went under the hammer to the Getty Museum in Los Angeles in 1995, only for the sale to be blocked at the last minute by the government at a cost of �7.6m.

Fund fears cash squeeze

In a bid to reduce numbers of treasures sold abroad, John Major's government set up the Heritage Lottery Fund. Part of its brief was to allocate grants to help preserve artefacts for the nation.

But independent art charity the National Art Collections Fund, which also gives grants to help British galleries compete, warns of increasing difficulties keeping treasures in the UK. It points to a rise in the failure rate of applications to the Heritage Lottery Fund.

Director David Barry said: "The Rembrandt will be a tough challenge and a real test case."

A bust of King Charles I by Francesco Fanelli was bought by the V&A for �240,000

Last month, the fund helped London's Victoria and Albert Museum raise enough money - right on deadline - to buy an historic bust of King Charles I.

"The case once again highlights a worrying trend, as it is one of several major acquisitions jeopardised following rejection by the Heritage Lottery Fund," said spokeswoman Annabel King.

"We have been officially told that Heritage Lottery Fund and National Heritage Memorial Fund money is being channelled away from works of art and diverted to cultural regeneration projects."

Less lottery cash

The Export Review Committee, which advises the government, has also expressed concern recently that most works for which it recommends export blocks do in fact end up being sold abroad.

But a Heritage Lottery Fund spokeswoman said since it began in 1995, museums and galleries had received the highest proportion of expenditure, with some �50m spent on acquisitions.

"We've been very generous - galleries have had more than 40% of all funds awarded by us. Our trustees support acquisitions and are keen on public access, supporting touring exhibitions, for example," she said.

"It's true the sum we gave in 1998 was lower but we had overall lottery income. Heritage is a wide subject and we have many demands, such as environment and industry and transport, but overall the fund has committed �524m to museums and galleries. In 1998, we funded 49 acquisitions."

"Let them go"

Meanwhile, the keep-it-in-Britain lobby faces another hurdle - those who question the value of their campaigns.

Last month, the founder of the Independent newspaper, Andreas Whittam Smith, was considered a heretic when he defended Marlborough College's decision to sell off a donated Gainsborough portrait - possibly abroad.

"If it could be estimated, I would expect to find that Britain possesses a greater treasure of art works than any country in the world, with the possible exception of the United States - even then, in relation to the size of their population, we in Britain probably come out well ahead," he wrote.