A unique festival celebrating a rare breed of seaweed-eating sheep is to be held on a remote Orkney island, when volunteers will help repair the wall that keeps them away from grass.

The fortnight-long event this summer has been organised by the community of North Ronaldsay to raise awareness of its ancient breed of shoreline dwelling sheep and to give people the opportunity to learn practical skills associated with managing the 3,000 strong flock.

According to the Orkney Sheep Foundation they are an ancient breed of small, hardy sheep, part of the family of short-tailed sheep found in various parts of northern Europe and on some of the Atlantic islands.

In the 1830s, the old pattern of land management was beginning to change in Orkney as elsewhere, with the formation of the modern field system and new methods of managing the island crofts. This opened up opportunities to grow crops and keep cattle, and to bring in bigger breeds of sheep such as Cheviots and Leicesters.

On many islands the native sheep did not survive these changes. But in North Ronaldsay a way was found to keep the breed which had served them well, while also embracing the new opportunities. A drystane dyke was built 13 miles round the island to keep them on the shore where they adapted to a seaweed diet.

The six foot wall also reduces the chance of gene-pool pollution of the flock through cross breeding with other sheep.

The diet of seaweed also makes them more susceptible to copper poisoning from island's grass, because it disrupts an enzyme in their system that absorbs the copper.

But now North Ronaldsay mutton is exported from the island and prized as a delicacy, thanks to its distinctive flavour. Wool from the sheep is also processed locally and sold to knitters around the world.

Maintenance of the coastal sheep dyke, which gets damaged by winter storms each year, is a continual challenge for the small community of just over 70 on what is Orkney’s most northerly island. Festival goers will help repair fallen sections of the wall, learning traditional building skills from local experts.

Volunteers are also being invited to take part in a North Ronaldsay punding - the process of rounding up the wild sheep from the beach in order to be clipped.

Festival organiser, Kate Traill Price, said: “The BBC’s Countryfile programme featured the sheep dyke earlier this year and highlighted our ongoing efforts to keep it maintained. Following that broadcast we were inundated with generous offers of help from people throughout the country, so we came up with the idea of the festival as a way of both utilising that assistance and highlighting what a wonderful place North Ronaldsay is.

“The festival is utterly unique and offers volunteers the opportunity to work alongside our community in conserving our rare and iconic breed of sheep,” she added. “It’s going to be a real hands-on experience, but also lots of fun, with many other activities planned during the two-week long event.”

The festival, which is supported by the Orkney Sheep Foundation, will run from July 25 until August 5.