GUARDIANS of the historic Rollright Stones are appealing for public help to stop arsonists who have targeted the ancient site four times in the past two years.

Karin Attwood, spokeswoman for the Rollright Stones Trust, which manages the 5,000-year-old Neolithic stone circle near Long Compton, said: "All these attacks happen at weekends, late at night or early in the morning. If anyone ever sees any cars near the Stones at these times, please take a note of the car number plate and phone the police or Crimestoppers."

Her comments follow the latest attack overnight last Saturday when the warden's office was broken into and a gas heater turned on and placed against wooden furniture.

This alarm was raised on Sunday morning when the site manager arrived to discover the lock to the office sealed with expandable foam and a small fire inside the building, which is a steel container-like structure placed at the site following two previous arson attacks on the warden's old office.

The Trust celebrated its 10th anniversary this year and Ms Attwood said she was concerned that the perpetrator or perpetrators of the recent attacks were determined to close the site down. "I would hate to ever see the site surrounded by barbed wire and closed to the public," she added.

The Stones' trustees sealed up the warden's office windows this week. Money was taken from the donation box during the incident.

The warden's office was severely damaged by fire in January 2006 and the office was vandalised and a burning tyre placed on one of the stones in two separate attacks in September this year.

The most serious vandalism occurred on the eve of April Fools Day in 2004 when bright yellow paint was splattered on each of 78 stones in the stone circle, causing an estimated £30,000 to £50,000 worth of damage.

PC Rob Kelly of Chipping Norton police station said: "We are becoming increasingly concerned about the welfare of this historically important site. Whatever the motivation behind these attacks, what it boils down to is wanton criminal damage and we are doing all we can to stop it; and we need the public's help in this."