It is one of the most prestigious showcases for Scottish art, where the Glasgow Boys, Charles Rennie Mackintosh and the Colourists have in the past displayed their painting, sculpture and drawing.

However, this year the Royal Glasgow Institute’s annual exhibition, now in its 150th year, has been hit for the first time in living memory by theft, with the loss of a bronze sculpture.

The sculpture of a horse, entitled Young Meggi, by John McKenna, was on sale for £1800. But it was stolen a day before the exhibition at the Mitchell Library in Glasgow ended.

Theft of metal has become endemic, police said earlier this year, with thieves increasingly stealing electricity pylons, gas pipes and even manhole covers, but Mr McKenna, based in Girvan, South Ayrshire, said the small bronze sculpture is likely to have been stolen for its value as a work of art, rather than for its metal.

Mr McKenna -- who works on architectural art as well as smaller works for private collectors, and whose many works include the statue of Jock Stein that stands outside Celtic Park -- said he is disappointed by the loss.

He believes a paying customer stole the sculpture -- based on one of his own Clydesdale horses -- and hid it about his or her person before walking out, past RGI staff at the door.

Mr McKenna said the work was a “one off” with no mould, and cannot be repeated.

As the RGI takes no responsibility for damage, loss or theft of art in the show, and because he is unsure whether his commercial art insurance covers theft from a public exhibition, the artist suspects the loss will not be compensated.

Established in 1861 to show the work of living artists, the RGI exhibition had been held annually at the McLellan Galleries in Sauchiehall Street until 2000, and is currently, on a temporary basis, at the refurbished premises at the Mitchell Library at Charing Cross.

Gordon Macpherson, president of the RGI, said the charity was “shocked and horrified” by the theft.

Mr McKenna added: “I have been exhibiting with the RGI for years so it’s quite a shock. It looks like someone has paid to get in and just walked off with it. You never would have thought someone would have the cheek to just walk in and steal it.”

Mr McKenna has informed Strathclyde Police about the theft.

Mr Macpherson said: “When the sculpture went missing on Friday, November 11, we contacted the police and the artist immediately. Whoever is responsible must have walked past both our reception desk and the attendant from The Mitchell outside the gallery. This is the first time in living memory work has disappeared from our annual show and would appeal to anyone who has any information to contact the police.”