The Brecon Beacons National Park Authority is highlighting the importance of heritage sites after a Bronze Age standing stone was vandalised in the park.

At some time over the last few weeks the Maen Llia standing stone, a Scheduled Ancient Monument situated on the high col just east of Fan Nedd , close to the Heol Senni - Ystradfellte road, has been graffiti-ed with a smiley face.

The iconic 3.7 metre tall standing stone attracts visitors from around the world, they say, and is recognised as a site of national archaeological importance. It is likely that the stone was erected in the Late Neolithic or Early Bronze Age between 2500 and 1800 BC.

Brecon Beacons National Park Authority is currently working with Cadw (the Welsh Government's historic environment service) and landowners to arrange for the graffiti to be sensitively removed - a slow and careful process undertaken by professionals who may have to use on-site trials to assess the most appropriate methods and materials.

Natalie Ward, Heritage Officer for Brecon Beacons National Park Authority, said:

'The heritage of the National Park is the legacy left to us by our ancestors and it contains a wealth of information about past peoples and their lives. The person who did this may well think it was harmless fun but archaeological sites like Maen Llia are fragile and causing damage to a Scheduled Ancient Monument is a criminal offence. Criminal acts like this can cause irreversible damage. Heritage sites and monuments don't belong to a single person, landowner or public body – they belong to all of us. We inherited them from our ancestors and it's important that we take care of these sites to pass on to future generations to enjoy.'

Martin Buckle, Brecon Beacons National Park Authority's Member Champion for Heritage, added:

'The vandalism that has occurred to Maen Llia standing stone cannot be condoned. You could compare it with spraying graffiti on a castle. It may be, however, that the perpetrator did not understand the site's importance. We hope that by highlighting this issue we can raise awareness of our ancient monuments and help protect them.'