The chairman of the charity looking after Oxfordshire's Rollright Stones believes one man is responsible for the arson attacks that have plagued the monument.

In September, vandals broke into the volunteers' office at the site near Chipping Norton, and daubed swastikas on the side. They also set fire to a stone in the stone circle.

On Saturday, they returned and used a crowbar to force shutters at the office before starting a fire inside.

Firefighters arrived before major damage was caused, but George Lambrick, chairman of the Rollright Trust, fears the perpetrator will return - and urged members of the public to report him to the police.

Mr Lambrick said: "There have been four arson attacks in the past three years and we believe one person is probably responsible.

"If anyone in the local community hears someone boasting about this, then they should report it to the police. The attacks are getting worse each time and they are potentially dangerous - we don't want someone to be injured.

"Part of the problem is that the site is extremely remote and we don't have any electricity. That means we have not yet been able to sort out CCTV, but we are looking into that very seriously."

Mr Lambrick said windows at the portable office were damaged and the floor was burned.

"Fortunately the fire brigade turned out very quickly," he added.

Anyone with information should call Pc Rob Kelly on 08458 505505.