Campaigners are bracing themselves for a fresh battle to save historic Athlone House in Highgate as its foreign billionaire owner has unveiled new plans for its demolition.

Determined residents fought for more than a decade to see off proposals to bulldoze the local landmark, which lies at the edge of Hampstead Heath.

But just a year after the government planning inspector rejected a controversial �80million project to build a state-of-the-art mansion on the site, its owners have launched a fresh application.

Gordon Maclean, chairman of the Heath and Hampstead Society’s planning committee, said residents were determined to “oppose this development to our last breath”.

He said: “We understand that the designs for the house are really very much the same as the previous designs, which we think were among the worst designs we have ever seen. We will oppose this development to our last breath.

“Athlone House is very important to the local community. The battle to save it really galvanised the community and I would expect similar scenes this time.”

Details of the design for the proposed mansion will go on show today (Thursday, July 19), and it will include a spa, cinema, ballroom and at least eight bedrooms - although a spokesman for the developers insisted the house is smaller than in previous plans.

Taking a combative stance, Mr Maclean warned that “a community gets very tired with developers who try again and again to do something which is unacceptable”.

Gordon Forbes, of the Highgate Society and Athlone House working group, said: Athlone House is a fine example of a Victorian family villa and was rich in architectural detail until it was allowed to fall into disrepair.

“It is well loved by the community.”

Built in 1870, Athlone House served as a residence to several prominent businessmen before being used as an RAF intelligence base and a hospital.

The fight to save it dates back to 2000 when it was first sold to developers who were given permission by Camden Council to build luxury flats on the grounds provided the house was restored.

It was sold again in 2005 to an anonymous foreign billionaire, believed to be a Middle Eastern ruler. But rather than renovate the house he wanted to replace it with what was billed as the world’s most expensive home.

Cllr Maya de Souza, who represents Highgate on Camden Council, urged its owner to stick to their original promise to restore the building.

In a statement the developers, Athlone House Ltd, said the only reason the planning inspector did not allow the development was that “he thought the building was too large relative to the existing one to be acceptable in policy terms on Metropolitan Open Land”.

They said the new designs addressed this concern.