Emergency support works have had to be carried out at one of the country’s most important heritage sites.

Support scaffolding had to be erected at Dun Aengus - Dún Aonghasa in Irish - on the Aran island of Inis Mór off the coast of Galway.

Engineers from the Office of Public Works travelled to the island within the last fortnight after it appeared a support wall for the prehistoric fort was collapsing.

The state of the wall, which was initially put in place at the end of the 19th century, had been observed some time ago but its condition had worsened recently.

The OPW said it had not been damaged by any single event or by tourist activity, but rather as a result of age and gravity.

National treasure

As Dun Aengus is officially regarded as a national treasure and is visited by hundreds of thousands of visitors every year, the temporary scaffolding work was installed without delay.

The Office of Public Works said it will carry out a more permanent structural repair later this year when the daily flow of tourists has eased.

Dubbed “the most magnificent barbaric monument extant in Europe” by renowned 19th century archaeologist George Petrie, the site stands precariously on the edge of a 100-metre high cliff on the western edge of Inis Mór, about 7km from Kilronan.

The entire area of the semi-circular fort comprises about 14 acres and it is thought the initial construction dates back to 1100 BC.

It consists of three irregular-shaped inner walls surrounded by a Chevaux-de-Frise, with a fourth outer wall covering about 14 acres.

The Chevaux-de-Frise is a mode of defence designed to thwart an attack. It consists of large, sharp limestone slabs sticking out from the ground at different angles, making it extremely difficult to navigate a way through.