A WORLD-RENOWNED stone circle in Orkney, which is more than 4000 years old, has been vandalised.

Damage to the Ring of Brodgar includes graffiti scrawled onto one of the stones at the Neolithic site near Stenness.

It is believed to have been caused sometime between Friday afternoon and Sunday morning.

Inspector David Hall said: “The stones at the Ring of Brodgar are priceless historical artefacts and the damage caused cannot simply be estimated in monetary terms.

“For someone to damage them in this way is a particularly mindless act.

“I would urge anyone who has visited the area over the last weekend to think back and if they believe they may have seen something suspicious, even if it didn’t seem of much note at the time, to let us know.”

The Ring of Broadgar was originally comprised 60 stones, with 36 surviving. It is in the Heart of Neolithic Orkney Unesco World Heritage Site on the islands’ mainland.

The site also includes the chambered tomb Maeshowe, the Stones of Stenness and the settlement Skara Brae. The ring was built around 2000-2500 BC and covers an area of almost 8500 square metres.

It is the third-largest stone circle in the British Isles – behind Avebury and Stanton Drew – and is the largest in Scotland.

One of the stones has already been vandalised, carrying a Norse runic inscription, while at least one other has been struck by lightning.

Celebrated visitors include Sir Walter Scott, who in 1814 wrote of the Ring of Brodgar and Stones of Stenness that “Stonehenge excels these monuments, but I fancy they are otherwise unparalleled in Britain”.

Historic Environment Scotland (HES) is aware of suggestions that the sites and monuments in the surrounding area were used for astrological observations from the Ring of Brodgar, but it is very hard to find conclusive evidence.

A HES spokeswoman said: “We would ask the public to be aware that causing reckless or deliberate damage to a scheduled monument is a criminal offence, and ask that anyone witnessing such acts report them to Police Scotland.”