A RARE copy of Charles Rennie Mackintosh's designs for his House For an Art Lover is expected to fetch thousands of pounds at auction after it was found in a house in Belgium.

Mackintosh originally submitted the design for an architectural competition for a "Haus eines Kunstfreundes" (Art Lover's House), set by a German design magazine in 1901.

The portfolio was disqualified for being late, but it was awarded a special prize for its "pronounced personal quality, novel and austere form and the uniform configuration of interior and exterior".

The house itself was finally built in Glasgow's Bellahouston Park in 1989 and opened to the public in 1996.

A rare copy of the portfolio, featuring prints of Mr Mackintosh's drawings heightened in silver, will go under the hammer at Bonhams in London on March 19.

Matthew Haley, Bonhams' head of books, atlases, manuscripts and photographs, said it had "international appeal" and could exceed its £8000 to £12,000 estimate.

Mr Haley said: "This rare contemporary reproduction was discovered in a house in Belgium. It had been passed down through the family of an architect and was gathering dust. Mackintosh designed his house for an art lover with his wife Margaret MacDonald."