A Hampstead pensioner claims her flat could be left sitting on stilts and turned into a “war zone” should plans to extend her neighbour’s £4.4million home be given the green light.

Proposals to overhaul the ground floor flat below Michele Bryan’s first floor home and build an extensive basement extension have been lodged with Camden Council.

The former teacher claims an application by Simon Sterling, who bought the five-bedroom flat off Redington Road, to demolish and replace a side extension, will leave her with a 20ft drop outside her kitchen door during construction.

The pensioner, who has lived in the flat with her husband David for 27 years, said: “They are going to dig out a huge basement while we are still living here and meanwhile we have to come and go and we will be in a hard hat area, a war zone.”

Mr Sterling bought the neo-Georgian flat last December and is bidding to enlarge the basement and replace two bedrooms with a gym and physiotherapy suite for his disabled son. He also plans to build a home cinema and a library on the expanded subterranean level.

Mrs Bryan, a former teacher at the City and Islington College, said: “They are going to dig out the basement, knock down all the internal walls while we are living here and it will take about two years. It will just be impossible.”

But William Smith, of Turley Associates planning consultants, representing Mr Sterling, said an impact assessment was carried out and showed that the work will not affect the structural stability of existing buildings.

He said: “The works are designed to improve the quality of the accommodation, which is currently run-down, to meet the accommodation needs of a disabled relative and to be in keeping with the character of the existing building and the local area.”

The road has been hit with countless developments. Actor Tom Conti has accused Camden Council of allowing it to be turned into an “industrial park”.