PAY ME £100 million, or your national art collection gets it." Thus might be paraphrased the demand by Francis Egerton, aka the 7th Duke of Sutherland, that he be paid £50m a piece for the two great paintings, Diana and Actaeon and Diana and Callisto, by the Italian Renaissance master Titian.

The National Galleries of Scotland (NGS) and National Gallery in London are engaged in a frantic "Titians Appeal" to keep the paintings on public display. Unless the duke gets £50m (for Diana and Actaeon) by the end of next month and £50m (for Diana and Callisto) by 2012, he is threatening to sell the entire Bridgewater Collection of 29 artworks - including the Titians and works by Raphael, Poussin and Rembrandt - which have been on loan to the NGS by the dukes of Sutherland since 1945.

Furthermore, the duke does not rule out letting the lot go to private buyers, rather than public galleries, even though parts of the Bridgewater Collection have been on public display in Britain since the early 19th century. Even if the £100m is raised, the duke only promises to lend the remaining 27 artworks for a further 21 years.

Has there been, in modern Scottish history, a more patent or shameful example of works of art being used to hold the nation to ransom?

The duke - who only came to his title in 2000, after the death of a distant cousin - is one of the richest men in the UK, with his personal wealth estimated in 2005 at £230m. Moreover, the Sutherlands owe a moral debt to the people of Scotland for the role their forebears played in the Highland clearances in the 18th and 19th centuries; the Sutherland clearances witnessed some of the worst atrocities of those catastrophic events.

Now - as Scotland shapes its post-devolution culture - would be a good time for the duke to gift the Bridgewater Collection to the people of Scotland; or, at the very least, extend the loan indefinitely. To do so would give him a proud place in history, towering above the ignominy of his predecessors.

The Bridgewater Collection forms the central pillar of the NGS's permanent exhibition of European art. Its loss would hugely impoverish Scotland both culturally and economically. The threat, not only to remove the paintings from Scotland's national galleries, but to take them from public view anywhere in the world, shames the Duke of Sutherland.