A RARE art treasure which could be worth up to £50,000 has been uncovered thanks to a hospital's X-ray department.

But celebrated modern artist Robert Lenkiewicz's picture of a tramp, hidden beneath an erotic image of a couple enjoying carnal knowledge, may remain beneath the more recent erotic composition.

The owner of the treasure, who lives in the Ashburton area and London but does not want to be identified, bought the two-in-one work at auction six years ago after Lenkiewicz's death in 2002.

But an art dealer soon guessed that the risque 'private' piece — showing the artist with one of his shapely models — hid an even greater prize underneath.

The collector had the nude couple X-rayed at Torbay Hospital to reveal a more valuable Lenkiewicz portrait of a tramp, a favourite subject of the famous South West artist in his early years.

The collector said: "The picture I bought could soon be valued at more than £50,000. It is a private work, which perhaps should never have gone under the hammer at the estates sale in Exeter in 2003."

But he added: "When the experts looked at it they reckoned it contained another picture underneath. So I took it to Torbay Hospital and discovered the tramp, which could be worth even more than what is painted over it!"

He has decided to relinquish his ownership of the masterpiece by selling it at the Driftwood Gallery in Padstow.

But he hopes the coupling picture is not tampered with: "I think the image there now is very good and rare. And it would be very expensive to ruin it just to get to the tramp."

Art dealer Adrian Phippen, a Lenkiewicz expert who suspected the picture's hidden portrait, said: "This is a very important piece of work by Lenkiewicz."

A South Devon Healthcare Trust spokesman said: "On rare occasions the hospital's radiology team will be asked to X-ray an object and when possible the hospital will always try to aid people.

"In this particular case the trust was happy to help and staff gave up their own time outside clinical hours to carry out this unusual request. They will be pleased to know that they have been part of such a remarkable finding.

"We would like to offer our congratulations to the owner of the painting, who must be delighted with this discovery. Where the trust has been able to assist, a donation to the trust fund is usually made."