Police are investigating after vandals daubed graffiti on a 5,000-year-old Neolithic chambered tomb.
Stoney Littleton Long Barrow, at Wellow near Bath, is a scheduled ancient monument in the care of English Heritage.
It is one of the country’s finest accessible examples of a Neolithic chambered tomb dating from about 3500 BC.
In early November, the walls of the tomb were daubed with red paint by vandals.
Avon and Somerset Police and English Heritage are now appealing for witnesses to the damage.
Win Scutt, properties curator at English Heritage, said: “Stoney Littleton Long Barrow is one of the country’s finest Neolithic chambered tombs, and this attack on its historic fabric is not only thoughtless, it is a crime.
“Whilst our specialist team will be working to remove the graffiti, there is every chance it might have caused permanent damage to the stonework.
“The motivation behind a wanton attack like this is unthinkable, and we have been working with Avon and Somerset Police to aid them in their investigations.”
Anyone with information is asked to contact Avon and Somerset Police on 101, using the crime reference number 5520250419.