A rare pair of rugs designed by the young Francis Bacon are to be auctioned.

Hand knotted shirt runner designed by Francis Bacon to be sold at the Netherhampton Saleroom, Salisbury, Wiltshire

It had been thought that only three of the painter's early carpet designs remained, including one held by the Victoria and Albert Museum.

But an auction house in Wiltshire claims to have found the only surviving works from Bacon's first exhibition of his own designs in 1929.

They were apparently donated by an Iranian carpet dealer who had cleaned out one of her storerooms.

Ian Bennett, a textile specialist at Netherhampton Salerooms, near Salisbury, told The Times newspaper that the donor was unaware of the rugs' significance.

He said: "This particular batch of rugs contained the usual mix of good, bad and indifferent, but there were a lot of them and initially they had to be gone through fairly quickly.

"All of a sudden, in the middle of a pile of Persian tribal weavings in varying stages of disintegration, there appeared two obviously European Modernist rugs, which I threw aside with an instant semi-automatic valuation of a few hundred pounds.

"Just as they were about to be covered up by other rugs, I vaguely noted the presence of writing at the bottom of each piece and suddenly what I had only half seen came into sharp focus. I said, 'Hang on a minute!'. In large capital letters was the name Francis Bacon."

He said the donor told him she had bought them ten years ago from an elderly lady who had been using them in her hallway.

He added: "She thought they were impractical. She kept on tripping over them. She didn't know what they were."

Bacon spent time as a furniture and rug designer in the late 1920s and early 1930s.

No records survive of the 1929 exhibition, but it was successful enough for Bacon to follow it up with a second one in 1930.

A year or two later he gave up design to concentrate on painting.

The rugs will be auctioned on March 12.