A High Court judge is set to rule on the future of historic Athlone House on the edge of Hampstead Heath today.

Ham & High: Athlone House, taken in 2011. Picture: Michael HammersonAthlone House, taken in 2011. Picture: Michael Hammerson (Image: Archant)

Mysterious developer Athlone House Limited (AHL) wants to knock down the former hospital and RAF base in Highgate and turn it into an opulent £80million eight-bedroom palace with underground car park and swimming pool.

It has now taken the secretary of state for communities and local government, Greg Clark, to the High Court after a government-appointed planning inspector dismissed an appeal earlier this year to overturn Camden Council’s decision to reject the plans.

If High Court judge Justice Ian Dove rules today (Thursday) that the 19th-century house is once again saved from demolition, it could change national planning guidance and set a precedent in law.

On Tuesday, a small but steadfast group of campaigners belonging to the Athlone House Working Group listened to evidence from both sides at a one-day hearing at the Royal Courts of Justice in central London.

Among them was Lord William Rodgers, the former leader of the Liberal Democrats in the House of Lords, who lives in Highgate Village. He said: “Athlone House is historic. It’s not a particularly distinguished building but it is significant and important and needs preserving against the hideous alternative. We have enough houses which cost anything between £5million and £15million but what we need is more houses for ordinary people to live in.”

In his landmark appeal decision in June, planning inspector Colin Ball ruled that plans for a mansion to replace crumbling Athlone House were “materially larger” than the existing building, and therefore under planning law, should be rejected.

But AHL disputes this and uses part of national planning guidance to argue that the house should be demolished.

AHL’s lawyer Robin Purchas QC wrote in his skeleton argument: “The inspector’s conclusions were wholly unsupported by the evidence.” He went on to conclude: “The decision should be quashed together with an order for the claimant’s costs.”

If Justice Dove quashes the argument, it could override a small part of planning law, setting a precedent.

Campaigners have been fighting planning applications to demolish the house since 2009.

The most recent proposal has been dubbed an “Arabian nightmare” and led to more than 5,000 people signing a petition for Camden Council to reject the plans – including Monty Python star Terry Gilliam.

They want the developer to stick to a historic section 106 agreement to restore the house to its former glory.

But AHL says the cost of refurbishing the mansion is too high.