Monty Python legend and film director Terry Gilliam has joined the campaign to save a historic Highgate house on the edge of Hampstead Heath from demolition.

Mr Gilliam, who lives in Highgate, has urged Camden residents to demand that the council throws out the latest application to bulldoze the 19th-century Athlone House and build an eight-bedroom mansion in its place.

The 73-year-old said: “Athlone House is the most wonderful building which can be seen from many parts of the Heath.

“It is an outrage that yet again we are faced with an application to demolish it. Camden Council should be forced to enforce the agreement to restore the house which was a condition of the development which has now taken place.

“I urge local residents and anyone who loves and enjoys Hampstead Heath to take 5 minutes out of their busy Christmas schedules to write or email Camden Council and demand that the owner restore Athlone House – it will be a tragedy to lose this building.”

The unknown owners of the 1870 building, in Hampstead Lane, filed a second application to demolish the house last month after the first was refused by the council in 2010 and the Planning Inspectorate on appeal in 2011.

The Highgate Society, which launched the campaign to save Athlone House, said it hopes around 600 people will write in to the council to oppose the demolition plans.

Members want the current owners to abide by an existing planning agreement that required the previous owners to restore the Victorian house after building a modern development of flats nearby.

Highgate Society member Liz Morris said: “It is critical that Camden Council understands how strongly residents oppose the destruction of this historic house.

“At the last appeal over 600 objection letters were sent and we need just as many again. The house is rich in architectural detail and it is the Highgate Society’s view that it is good enough condition to restore if the will is there – which clearly it is not.

“Please send your letters and emails to Camden Council addressed to Charles.thuaire@camden.gov.uk or [give them] to him at 6th floor, Camden Town Hall Extension, Argyle Street, London, WC1H 8EQ, quoting reference 2013/7242/P by December 31st”.

An Athlone House spokesman said: “It is unrealistic to expect the new owner to implement the existing planning consent given the very poor condition of the building and the need to provide a very high quality living environment to meet today’s standards.

“The Planning Inspector accepted this reality and concluded that a new house would be acceptable subject to a high standard of design, which we believe Robert Adam has produced.”