An iconic painting owned by a major whisky firm is to go under the hammer.

The Monarch of the Glen by Sir Edwin Landseer is expected to fetch up to £10m when it goes to auction at Christie's in London next month.

Its owners, whisky giant Diageo, said the 1851 painting, which has been on loan to National Museums Scotland since 1999, had "no direct link" to its business.

The drinks company also confirmed it would gift another painting - the Thin Red Line by Robert Gibb - to National Museums Scotland.

A Diageo spokesman said. "Our ownership of the Monarch of the Glen is an historical legacy which has no direct link to our business or brands.

"We have made a major contribution by loaning the work for the past 17 years, but we believe the time is right for us to pass on the ownership of the painting.

"The priority for Diageo is to ensure all our assets are focused on growing our business and delivering value for our employees, shareholders and the communities where we operate."

A spokesman for National Galleries Scotland said: "The Monarch of the Glen by Sir Edwin Landseer is a well-known painting which has been on public view for many years as a loan to National Museums Scotland.

"The familiar image of the stag is an important Victorian picture that has taken on various layers of meaning, which include its use in advertising and as a Romantic emblem of the Highlands of Scotland.

"This painting will undoubtedly draw attention now that it is up for sale."

He added: "NGS always carefully considers any paintings with a strong Scottish dimension that come on to the market but for obvious reasons we never comment on our potential interest ahead of a sale."