Basement developments in Hampstead Garden Suburb will only be allowed under the largest detached homes, according to new rules issued following a High Court battle waged by a former banking tycoon.

Ham & High: Richard Wiseman. Picture: Nigel Sutton.Richard Wiseman. Picture: Nigel Sutton. (Image: © Nigel Sutton email pictures@nigelsuttonphotography.com)

Hampstead Garden Suburb Trust, which rules on every development application in the conservation area alongside Barnet Council, has issued new guidance to residents which stipulates that basements will generally not be allowed beneath terraced, semi-detached or “modest” family houses.

Residents living in cottages and “closes or narrow roads” are also unlikely to be granted permission to build a basement.

The limit for basement excavations, under the new rules, is one-storey, or three metres, and will be allowed to cover the entire footprint of the home.

The long-awaited publication of the new rules follows a series of court battles between the trust and Suburb resident Sir Victor Blank, a former Lloyds Banking Group chairman, which have helped to clarify the trust’s powers to regulate basement developments.

In 2013, Sir Victor, 72, instructed lawyers to obtain a High Court injunction stopping the trust from making a decision on neighbour Scott Franklin’s proposed basement swimming pool.

Sir Victor was backed by a group of 12 neighbours, including judge Sir Brian Leveson and TV presenter Richard Madeley.

His fight was eventually thrown out by the Court of Appeal last year, landing him with legal fees running into six figures.

The trust has spent the subsequent 18 months reviewing its basement policy in light of the court judgements and finally published its guidance this week.

Trust chairman Richard Wiseman said: “The trouble with basements is there is no consistent view with our residents. A large number would like to have a basement and won’t oppose them and a lot of residents oppose basements wherever they are.

“In the right part of the Suburb our guidance will continue to allow substantial basements. I think what we have put out strikes a balance between those who are seeking appropriate basement developments and the needs of the community.”

Reacting to the new rules, Sir Victor, 72, who lives off Wildwood Road, told the Ham&High: “This is a very positive move forward for the protection of the Suburb and its residents.

“It’s very important that the trust fairly, even-handedly and consistently enforces its guidelines.”

In March last year, Mr Franklin’s basement application was rejected by the planning inspectorate after a five-day inquiry. The planning inspector refused permission for the basement due to the damage it would do to a tree.

The trust was set up in 1968 to preserve the character of the Suburb, which was founded by Henrietta Barnett as a “model community for people of all classes living together in beautiful houses”.

From next year, Camden Council is set to ban so-called “mega basements” beyond one-storey but there are no plans for Barnet Council to do the same.