A drill used by vets on animal teeth could be used to clean paint from an ancient Oxfordshire monument.

The idea is to be tested this week at the Rollright Stones, a 3,500-year-old circle of stones set in open countryside near Chipping Norton.

They were daubed with yellow paint earlier this year and trustees have been trying to find the best way to remove it without causing further damage.

Following a visit to the dentist, the wife of one of the trustees suggested an ultrasound drill used to remove plaque.

Site manager Don Prout, pictured, said: "Nobody has tried this before, but we are going to give it a go. It will be the last of many tests we have been carrying out and, who knows, it could be the solution."

Chipping Norton vet Peter Aylmer has agreed to bring along his portable equipment on Wednesday and carry out a sample test on a small piece of stone.

He will have to use distilled or collected rainwater -- to prevent the chance of any mineral reaction with the stone -- and plug his machine into a generator.

English Heritage staff, who has been closely following previous tests, will be there to observe.

Police are still seeking the vandal who daubed yellow paint on the historic stones on April 1 this year -- an attack which experts feared could cost up to £250,000 to remove.

Their most promising lead so far has been a CCTV picture of a man covered in splashes of yellow paint, taken at the petrol station at the Chipping Norton roundabout on the A44 on the same day. But he has not yet been identified.

Mr Prout added: "We are trying equipment used by vets because animal teeth are generally smaller than human ones.

"The manufacturers have already carried out a test to remove paint from a tin can without damaging it, so we are hopeful.

"The stones were likened by a 17th century historian to stumps of teeth coming out of the ground, so maybe it could be the answer."