PENTRE Ifan has stood for over 5,500 years but it has taken up to the 21st century for it to have been vandalised.
Now police, National Park Authority and Cadw officers are investigating the damage including graffiti, which has been painted on the ancient burial chamber near Nevern. Police are appealing for information to find those responsible.
PC Esther Davies, of the Dyfed-Powys Police rural crime team, said: “We are saddened by the vandalism to the Pentre Ifan burial chamber. This is one of the most famous prehistoric sites in Wales, and it is unacceptable that someone has done this.
“Not only have they damaged the monument, but they have caused significant damage to the lichens growing on the stones.
“Cadw are working closely with us, and will be dealing with the removal of the paint.
“We would urge anyone who has information about the culprit to contact the Rural Crime team by calling 101.”
Proactive patrols are being carried out by officers, in partnership with Cadw and the Pembrokeshire Coast National Park Authority, at other sites of historic importance to ensure no further damage is caused elsewhere.
Inspector Roger Smith, Heritage Crime Liaison Officer, said: “We take heritage crime such as this very seriously within Dyfed-Powys.
“Pentre Ifan is a scheduled ancient monument of immense national and international significance, and we are investigating the damage to it as a priority.
“We are working closely with our colleagues from both Cadw and the National Park Authority. We are currently piloting a proactive Heritage Watch programme within the National Park, where police officers and PCSOs, together with Cadw wardens and National Park Rangers, are patrolling heritage sites in order to prevent damage and antisocial behaviour.”