The Big Question: Should Turner's 'Blue Rigi' and other masterpieces be saved for Britain?

Why are we asking this question now?

Tate galleries have launched a campaign to buy The Blue Rigi, a late-period watercolour by the great British artist JMW Turner. The work was sold at auction in June to an anonymous bidder who paid £5.8m - three times the expected price. The new owner was required under British laws to apply for an export licence to remove the work from UK.

The body responsible for considering the application, the Reviewing Committee on the Export of Works of Art and Objects of Cultural Interest, awarded the painting a starred rating - the highest level of protection - and recommended the export be deferred.

The Culture Minister, David Lammy, responded by imposing a temporary export ban on the painting, giving organisations until March 2007 to match the price paid at auction in the summer to keep it in the UK. Unfortunately, Tate has only £2m to put towards the purchase, and is looking to the publicly funded National Heritage Memorial Fund and the Art Fund, an independent charity, to make up the difference.

Why does The Blue Rigi matter?

Turner's painting is one of three studies of the Swiss mountain at Lucerne examining the effects of light at different times of the day. All three - Red, Blue and Dark - will be brought together for an exhibition at Tate Britain in January. Supporters of the purchase say not only is the painting one of Turner's finest - and the most important watercolour to come on the market for 50 years - but it is world class.

Committee members considering its export declared it not just to be outstanding in terms of its technical accomplishments, but also to be of vital importance to the study of the artist. While the existence of preparatory sketches, part of Tate's vast Turner Bequest left for the nation by the painter, provided an "exciting context" for future scholarship. An export ban imposed on The Dark Rigi already saved the painting for the nation in the summer. The Red Rigi, however, is owned by the National Gallery of Victoria in Melbourne Australia.

What is the law?

Ministers were empowered under the 1939 Export Control Act to intervene on behalf of the nation to prevent items of cultural, economic or technological value leaving the country. A committee run by the Museums, Libraries and Archives Council was established in 1952 to advise the Government on decisions relating to the export of cultural objects. It may consider up to a dozen applications a month from buyers wishing to export items from the UK.

Made up of eight expert permanent members, the panel is responsible for all types of cultural treasures - from paintings to decorative arts, manuscripts and archaeology. The law was updated in 2002 after recommendations made in the Scott report in the wake of his arms-to-Iraq inquiry.

How do they decide what should be saved for the nation?

Decisions are based on the three so-called Waverley Criteria, a set of rules named after the 1st Viscount John Anderson, who was Chancellor of the Exchequer in Churchill's War Cabinet and who gave his name to the wartime shelters, not to mention the inventor of PAYE.

To satisfy the criteria and to qualify for an export bar, an object must be more than 50 years old and closely connected to British history and national life. It must be of "outstanding aesthetic importance" and contribute to the study of art, learning or history.

What happens next?

Unfortunately, the review process, widely regarded as robust and effective, is only half of the story. Once an item meets the Waverley criteria and the minister has acted, it is up to someone to come forward with the cash. Sometimes, when a serious British buyer is at hand, the deadline can be extended, but often it is not. In an art and antiquities market where prices are soaring and new records are being set at auction each month, Britain's relative ability to afford important pieces is declining rapidly. Cultural groups have watched in horror as treasures and masterpieces disappear into overseas collections, denuding the nation of its cultural heritage.

What has been saved and lost?

Concerns over disappearing treasures reached a head in 2002 when the Duke of Northumberland announced that he was to sell his Raphael Madonna of the Pinks, which hung in the National Gallery, to the J Paul Getty Museum in California. After a huge public row, and a temporary export ban, the work was saved at the cost of £22m after the intervention of the Heritage Lottery Fund. The following year an anonymous benefactor stepped in to save Sir Joshua Reynolds' £12.5m Portrait of Omai for Tate, after a campaign led by Sir David Attenborough, chair of the Art Fund's Centenary Committee.

But while the most famous items, which gain the most publicity are often saved, it is not always the case for lesser-known pieces, which can slip quietly away unnoticed. Of the 27 temporary export bans imposed in 2005-06, items ranging from historic Naval medals to a George II Gothic painted cabinet attributed to William Hallett to Naddo Ceccarelli's The Madonna and Child were lost.

What can be done to improve the system?

The Art Fund is asking the Treasury to introduce a new tax break that would give 40 per cent income tax relief for any individual donating a work of art or artefact to the nation. Yet this would still leave Britain lagging far behind the US, where 100 per cent tax relief is available, or France, where 90 per cent tax breaks are available. Some favour the establishment of a national fund. A lump sum of, say, £500m, invested at the end of the last recession, would have yielded sufficient returns to have seen off all the export crises of the past 10 years and allowed museums and galleries to build collections in new areas.

Should we worry about works of art going to collectors abroad?

Yes...

* Art is such a vital part of our national heritage and so central to our culture that the Government has an obligation to protect it

* British museums are being overwhelmed by US institutions with deep pockets, which increases the need to protect what we have

* World-class collections in British museums and galleries help boost tourism and make the UK an important academic centre

No...

* The art market is just like any other, and artworks should be traded freely and openly without the interference of governments

* Many of the finest pieces in British galleries and museums are by foreign artists and were themselves acquired overseas

* It is better for pieces to go on show to the public overseas than remain in private collections in Britain