Masterpieces adrift on the tide of power and money

Yet the paintings' history suggests that a globalised art market is nothing new and their changing ownership reflects the rise and fall of Europe's great powers.

Titian first offered to produce the paintings part of a series based on Ovid's poems for the Holy Roman Emperor in the late 1550s but they were eventually sold to the Spanish king Philip II, the greatest monarch in Europe. And in Madrid the masterpieces formed the centrepieces of what was then the world's most spectacular private collection.

By 1704, however, Spain was in deep decline. Hoping to win French support, Philip V offered the paintings to the French ambassador. So they passed into the collection of Philippe, Duke of Orleans, nephew of Louis XIV and one of Europe's most powerful men.

But this home, too, proved only temporary. With France engulfed by revolution in 1789, the new Duke, Louis Philippe, hastily got rid of his art collection to a Brussels art dealer. He promptly put the Titians up for sale in London, and in 1798 five years after Louis Philippe lost his head they were snapped up by Francis Egerton, the third Duke of Bridgewater.

Like many British nobles of the day, Bridgewater had been on the Grand Tour in his youth and regarded Italian art as the height of civilisation, But he was also a new kind of aristocrat a wealthy coal magnate, known as the "Canal Duke" after building Britain's first modern canal between Worsley and Manchester.

Only a few years later, Bridgewater bequeathed the Titians to his nephew, Earl Gower. And it was Gower who first put them on show, exhibiting them in a London townhouse in 1806 to huge acclaim. "I was staggered when I saw the works," wrote the essayist William Hazlitt after one visit. "A new sense came upon me, a new Heaven and a new Earth stood before me."

The paintings have been on display ever since, moving to Edinburgh on the outbreak of the Second World War and impressing artists and visitors alike. Lucian Freud even called them "the most beautiful pictures in the world".

It would be a shame if they left these shores but, in truth, it would not be a national disaster. After all, the paintings have already travelled far from their native Venice. They have always followed the tides of power and money. And if that means swapping Scotland for Shanghai, then, sadly, so be it.