ONE of Scotland's leading businessmen has harshly criticised the decision by drinks giant Diageo to sell the £10 million masterpiece The Monarch of the Glen - among the most celebrated artworks in the country.

The drinks firm announced last week that it would sell the famous piece, created by English painter Sir Edwin Landseer in 1851, at Christie's auction in December because it had "no direct link to our business or brands".

Now renowned banker Sir Angus Grossart, a key figure behind the £66m revamp of the Burrell Collection, has branded Diageo "unworthy" of the feted artwork and in a letter published in today's Herald described the sale as a "slap in the face".

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And the former vice-president of Royal Bank of Scotland demanded that "noble Scottish prince" should be gifted to a public institution for free.

He writes: "This decision should be reversed by the board of Diageo, and before it becomes a major public issue."

Sir Angus compared the international display of the artwork before putting it under the hammer as akin to "a captured prince being taken to Rome to be sold for the highest price, to any buyer".

He said the decision to sell the oil-on-canvas "seems like a specious rationalisation of a procurement decision, rather than a considered group decision of the reputational and Scottish issues involved."

But Diageo argued that they have loaned historic works of Scottish galleries and recently gifted a key piece to the country.

The Monarch of the Glen had been was on loan for 17 years to the National Museum of Scotland.

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Sir Angus, chair of Noble Grossart, is a former vice chairman of the Royal Bank of Scotland and has served as a chair of the National Museums of Scotland, the National Galleries of Scotland, and the Heritage Lottery Fund and is still deeply involved in cultural affairs: he is chairman of Lyon & Turnbull, the Burrell Renaissance and the Edinburgh International Culture Summit.

He said Diageo's decision to sell the painting "has to be challenged, and changed".

In the letter he comments on the "highly contentious" takeover of The Distillers Company by Guinness in 1986, and how the painting became owned by Diageo, which was itself formed in 1997 from a merger of Guinness and Grand Metropolitan.

Sir Angus writes: "Great significance was placed in the repatriation of the Monarch to Scotland, where it became a major feature in the head office in Edinburgh, and reinforced the senior executive presence in Scotland.

"Over time, the painting was freely lent or made available, always in a context which presented Diageo as a committed corporate participant in Scottish public and cultural life.

"This was not symbolic but was promoted strongly as confirming the integrity of their intentions and an acknowledgement of their wider responsibilities, as a major company in Scotland."

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Sir Angus concludes: "Is it to raise £10m for a company which is capitalised at £52bn? It beggars belief that the board has endorsed this proposal....It is hoped that a more considered judgement, and wiser counsel will prevail, before this is allowed to happen."

A Diageo spokesman said: “We have recently announced that we are gifting the Thin Red Line by Robert Gibb, acknowledged as one of the most important works of Scottish military art, to National Museums Scotland on behalf of the nation. We have also confirmed that the Macnab by Sir Henry Raeburn will remain on loan to the Kelvingrove Art Gallery in Glasgow. Therefore, Diageo is responsible for two major works by Scottish artists being available to public view, which we believe is a significant cultural contribution in Scotland.”