Stop the owners of historic houses in Hampstead from permanently damaging the area’s heritage before it’s too late, say conservationists.

Ham & High: Marganita Laski lived in Capo di MonteMarganita Laski lived in Capo di Monte (Image: Archant)

Members of the Heath and Hampstead Society have accused Camden planners of being “too scared” to block schemes which do irreversible harm to listed buildings because of the threat of expensive planning appeals from rich owners who can afford top lawyers.

This comes as planning officers have recommended members of the development control committee tonight approve plans to replace a conservatory with a new extension and build a basement gym and cinema complex under the historic Grade II listed Capo Di Monte house, in Windmill Hill – once home to 18th century Shakespearan actress Sarah Siddons and later to writer Marghanita Laski.

It also comes as plans have been submitted to build a basement under a Georgian house in Rosslyn Hill, behind the Windmill Hall recording studios, described by the society as “one of Hampstead’s hidden masterpieces.”

David Castle, chair of the Heath and Hampstead’s planning subcommittee, said: “This has got to stop. The owners of these historic homes should be aware that they are custodians of our rich history and heritage. They should not be allowed to damage these houses with plans for extensions and basements.”

Mr Castle welcomes moves by Camden to introduce a blanket ban on the construction of basements under listed buildings and to limit all basement excavations to one storey. But he believes by the time the policy becomes law in 2016 it could be too late.

He urged the council to start making decisions in line with these proposals now. He said: “It is unlikely the basement policy will be agreed before next year. They should use it to start refusing applications now. But they seem to let these schemes go through as they are too scared of the cost of fighting an appeal.”

The plans for Capo Di Monti, which dates from the late 18th Century, extending a previous basement by 72sqm to include a library, gym, and cinema room with lightwells under the house and garden. Officers have recommended approval after the scheme’s footprint was reduced.