Diana and Actaeon, 1556-59, Courtesy National Gallery Scotland. Lent by the Duke of Sutherland in 1945

In the first ever collaboration of its kind, the National Gallery, London, and the National Gallery of Scotland are joining forces in a bid to preserve the historic Bridgewater collection.

The extensive collection, which includes masterpieces by Raphael, Rembrandt, Poussin and Titian has been on continuous public view in the National Gallery of Scotland since it was placed there on loan by the then Duke of Sutherland, the 5th Earl of Ellesmere, in 1945.

But now an announcement by the current Duke of Sutherland has put the future of the holdings under threat, unless the galleries can raise £100 million to buy two of the most important works in the collection by Titian.

The Duke declared his intention to sell off the paintings after a ‘prudent review’ of the family’s assets. However, the Titians, which reportedly have a combined market value of £300 million, are being offered to the galleries at the reduced price of £50 million each.

The offer comes with the further assurance that a successful purchase of the Titians would secure the long-term future of the entire collection.

Diana and Callisto, 1556-59. Courtesy National Gallery of Scotland. Lent by the Duke of Sutherland in 1945

If the bid to raise funds to buy Diana and Actaeon is successful by December 31 2008, the second painting, Diana and Callisto, will be offered for sale in four years time. The galleries would then display the Titians on an alternate basis in Edinburgh and London.

Nicholas Penny, Director of the National Gallery, London described the £100 million combined offer as "remarkably advantageous".

He added: “For a century, the agitation to preserve great works of art in British collections from export has been animated by anxiety that Titian’s great paintings might be sold. Their acquisition by both institutions would be an historic event.”

The paintings were created as part of a cycle of works for Philip II of Spain and are seen to represent a high point in Italian Renaissance art. They each illustrate Greek myths involving the wrath of Diana, chaste goddess of the hunt.

John Leighton, Director General of the National Galleries of Scotland commented: “The Bridgewater loan is the most important Old Master painting loan to any public museum in the world and is of supreme importance to Scotland and the rest of the UK.”