Private home basement works create fears of more flooding Other residents reported flooding and damp in their basements when works began in 2010 to develop the vast underground quarters. They believe the flooding may have taken place because of the large basement blocking ground water level. Plans for further works at Witanhurst Mansion were submitted to Camden Council last month. Elspeth Clements, Highgate Society planning and development chairman, said: "We are hearing a lot of tales about basements. What we are trying to do is to get information and evidence from people affected so the council is more careful in approving basements next time. The council said anyone who wants to develop their homes underground must submit a Basement Impact Assessment explaining the effects of the proposed development. Witanhurst Mansion is the largest private home in London outside Buckingham Palace. Developing basements has become common in parts of London, where space is at a premium, but is spreading across the country. Sarah Beeney, the Property Ladder presenter, recently told the Sunday Telegraph: "Everyone has gone basement mad." The practice is particularly popular in Hampstead and Kensington, where underground extensions to lavish properties have led to them being dubbed "iceberg homes." These super basements often contain a variety of extra features, including ballrooms, swimming pools, spas and cinemas. The number of planning applications for works to develop basements submitted to Kensington and Chelsea planning department has soared in recent years, as a number of wealthy home owners further extend their properties underground.