The biggest art robbery in UK history

The theft left the Duke of Buccleuch, who owned the painting, heartbroken. It had been in his family for more than 250 years, but was stolen in broad daylight from his ancestral home.

It was a month to the day after his death, and four years after it was stolen, that the £30m painting - the finest in the duke's collection - was found.

"How sad it seems," an expert in art theft with great knowledge of the case said last night, "that it was found now, and not a month ago."

Last night Sir Timothy Clifford, the former director general of the National Galleries of Scotland and expert in Renaissance art, told The Herald: "Although we must rejoice and be very, very relieved that it looks to have been found, it is so, so sad that the last Duke of Buccleuch passed away before it was recovered. It is one of the finest works from the Renaissance period in the country. It is a really big thing."

The duke, born Walter John Montagu Douglas Scott and one of Britain's biggest landowners, died after a short illness a month ago, aged 83, still the victim of a theft which pained him sorely.

Only last year, the theft had moved up to seventh on the FBI's own art crime list, and its image was displayed prominently on its website.

The case appeared on the BBC's Crimewatch two years ago, but until last night no developments had been announced or reported.

Sir Timothy added: "There were so many rumours when it was stolen. I know the duke was hit very hard by its loss.

"But these paintings do appear again, because they are impossible to fence' - they are so difficult to sell on in the black market, because they are so famous and well-known.

"The most important thing is that all important paintings of this type are properly photographed and we know where they are. And I may say, if it is not too cheeky of me, that if it is recovered, it could be loaned to the National Galleries of Scotland."

The painting shows a young, beautiful Madonna with a child Christ holding the winder, which alludes to the domesticity of Mary and the child's eventual fate on the cross.

The Madonna has a disputed history, although Leonardo is thought to have worked on it between 1500 and 1510 for the Secretary of State to French King Louis XII.

There are two versions of the painting and it is not agreed among experts how much work Leonardo did on either. The other version is in the US.

The Buccleuch estate holds one of the UK's finest private art collections, worth £400m, including masterpieces by Rembrandt and Holbein.

In the robbery, on August 27, 2003, two men dressed as tourists overpowered a young guide and stole the painting from its display cabinet.

With two accomplices, they escaped in a white Volkswagen Golf abandoned nearby.

It has been speculated the painting may have been damaged in the process, as its frame was removed.

Experts in art theft have long said they believed the painting was still somewhere in Scotland, rather than in London or abroad.

Unless stolen "to order", the fame of the painting and the magnitude of its theft would have made its sale on the black market very difficult. The painting, experts say, was likely to have been hidden in a small space, but could not have been rolled up - it is oil-painted on to board.

Julian Radcliffe, chairman of the Art Loss Register, said: "If you had asked police in 2003 whether this was likely to be recovered, they would not have been optimistic. It is fortunate it has been recovered so quickly. It is very difficult for people to sell art of any value on so the main question is why people steal it in the first place."

Whatever the details of the case, the Buccleuch family have been lucky - some major art thefts are never resolved. The Isabella Stuart Gardner Museum in Boston was hit by a huge art heist in 1990. Among the pictures taken were a Vermeer, two Rembrandts, and a Degas.

The Art Loss Register in London records more than 180,000 stolen artworks on its database.

Its statistics show that only 15% are recovered in the following 20 years.