The scourge of basement conversion has driven one of London's most famous couples – Charles Saatchi and Nigella Lawson – to put their £36m Chelsea home up for sale.
This week, it emerged that the owners of the property next door to Saatchi and Lawson's Eaton Square home have put in an application for a huge amount of renovation work, including a basement extension under the garden. The work would also involve removing interior walls and parts of the back wall.
This follows hard on a dispute between the reclusive Saatchi and the owners of the apartment immediately above theirs, which culminated in the police being called. Scaffolding at the rear of their stucco house annoyed Saatchi so much that, after his appeal for it to be taken down had fallen on deaf ears, he hired his own workmen to remove it.
He was accused of causing £50,000 worth of damage to Italian marble tiles. The police came round to investigate, but went away after deciding that it was a civil matter.
Now the couple have decided to move, rather than put up with more hassle. Despite the recession, they are hoping to sell for almost 10 times the £3.8m Saatchi paid when he bought the house nine years ago.
In the most fashionable part of London – where every square foot of land is worth eye-watering sums of money – the cheapest way to increase your living space is to dig down. For a fraction of what it would cost to buy somewhere bigger, you can add an extra room or even double your living space by renovating a basement and extending it out under the garden – but at the risk of seriously annoying the neighbours.
Saatchi, 67, is well known as an art collector as well being the co-founder, with his brother, Maurice, of one of the world's largest advertising agencies.
He and Lawson married in a private ceremony in Belgravia in 2003. Both had been married before. Lawson is renowned as a celebrity chef, though she shrugged off the title of "Domestic Goddess" when she was speaking at the Cheltenham literary festival yesterday, saying that it was only "tongue in cheek".
The couple live in an apartment made up of the ground floors and basements of two adjacent mews houses that have been knocked together. The top three floors belong to an Egyptian family.
The hazards of basement conversion were graphically brought home last week to the residents of Chester Row, in Belgravia, near where Margaret Thatcher and the Chelsea FC owner Roman Abramovich live.
A firm called The Big Basement Company was carrying out a conversion on a home which changed hands last year for £2.9m, putting soil and debris from the excavation into a skip in the road, when the road gave way and the skip fell through into a storage vault.
The builders said the road had been weakened by a water leak. Neighbours blamed the council for allowing the conversion to take place at all.
One of the best-known basement converters was Andrew Lloyd Webber, a fellow resident of Eaton Square, who bought the house next door, dug down and connected the two with tunnels. David Cameron also commissioned some extra basement space in his North Kensington home four years ago, when he was opposition leader.
Having the work done can cost up to £300 per square foot, or £120,000 for a 20ft by 20ft basement, which is a cheap investment in a part of London where it is hard to find any property selling for less than £5m.