The wind howled and the rain poured but campaigners determined to save Athlone House from demolition were undeterred in their last-ditch effort to get residents to join their fight.

Three members of the Highgate Society asked windswept walkers to object to the latest plans to demolish the 19th century building, on the edge of Hampstead Heath near Highgate, on Sunday.

Catherine Budgett-Meakin, Richard Webber, head of publications, and environment committee member Michael Hammerson braved the bad weather to tell passers-by about proposals to knock down the former RAF intelligence base and hospital and replace it with an eight-bedroom home, with basement car park and swimming pool.

Today is the last day residents can write to Camden Council with their thoughts and Ms Budgett-Meakin, 67, is leading the campaign to get people to have their say.

“I think the developer is just trying to grind us down. Hampstead Heath is not just a London thing, it’s a British thing and Athlone House is part of that,” said the Bisham Gardens resident.

“Standing on the Heath in this freezing, dirty weather is not something I would choose to do but every time I have done it, I have been bowled over by people’s outrage at what is going on and how they feel that the developers and planners are reworking the planning system.”

Objectors to the planning application say that the developers should stick to a historic agreement requiring the previous owners to restore the derelict house to its former glory.

They criticised the council for being “feckless” in allowing planning applications to be submitted and not forcing the owners, Athlone House Limited, to refurbish the house.

A spokesman for Athlone House Limited 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.”

A spokesman for Camden Council said: “The Section 106 agreement required Athlone House to be renovated within 42 months of work on the construction of flats in Caenwood Court. While any application or appeal is on the table, it is almost impossible for the council to convince a court to sanction enforcement action. Throughout the entirety of this process the council has been conducting regular checks of the property to ensure the owner is complying with the obligations which ensure that the property is secure, as well as wind and water tight to avoid further deterioration.”

Hundreds of people have written to the council voicing their thoughts, with thousands more signing the Highgate Society’s online petition objecting to the planning application.

Kirsten de Keyser, Highgate Society chairman, said: “When you talk to people, they say it won’t make a difference [to write in to the council] but massive volume is ammunition for the councillors.”