Billed as the most beautiful mansion in Ireland, Russborough House was tonight placed on a global list of endangered sites.

The 18th century mansion at the foot of the Wicklow mountains has been named by the New York-based World Monuments Fund as at risk.

The heritage group warned most original outbuildings, 18th-century water features and historic structures in the demesne are in urgent need of repair.

The fund said the bridge to Lady’s Island, the lime kiln, and the ice-house had suffered the most.

“Loss of historic natural features, including mature broad-leaved woodland and parkland trees, is a very serious problem that must be met by a vast and well-researched replanting program,” it warned.

Russborough’s chief executive Eric Blatchford plans to develop the historic mansion and grounds for music events, weddings and sport.

The estate is also being promoted as a film and television set. The stately home sits near the Blessington lakes and was built by Joseph Leeson, first Earl of Milltown.

Conservative politician and honorary Irishman Sir Alfred Beit bought Russborough in 1952 as a home for the Beit Collection.

In 1976 he established the Alfred Beit Foundation and in 1978 the house was opened to the public.

PA