He is lucky; most new basement owners seem to make mortal enemies of their neighbors. The projects “are for today’s Chelsea residents what cholera was in the mid-19th century — a miasma lurking invisibly, waiting to pounce,” Terence Bendixson, honorary secretary of the Chelsea Society, a civic group, told The Evening Standard recently.

London has strict zoning laws and forbids in many cases changing the footprint of a house or adding to its height.

But the law was written only “with that which takes place above the ground in mind,” Tony Hillier, the chairman of the Heath and Hampstead Society, a civic group in North London, said in an interview. Using a British colloquialism for “flout,” he added: “A number of people who seek to develop underground have been able to drive a coach and horses through the law by saying it doesn’t actually prevent you from digging almost to the center of the earth.”

In a city in which rich people endlessly buy new houses and then renovate them, construction rage is not a new phenomenon: even Londoners who have refurbished their own properties tend to react with righteous indignation to their neighbors’ refurbishment efforts. But anger over the classic grievances — noise, extra traffic and maybe some dust — is small potatoes compared with the white-hot fury provoked by excavations.

“The past year has been a nightmare,” Matthew Wright, a popular television and radio host, wrote recently in The Daily Mail, describing the basement project next door. So bad was the “excavation, foundation drilling, concreting, underpinning (you want to try to live through underpinning), not to mention shuttering, grinding, drilling and so on,” he said, that even earplugs “meant for shotgun enthusiasts” could not drown out the noise.

Unable to sleep after the workmen arrived at 7:15 every morning, wielding pneumatic drills that caused his bed to vibrate, Mr. Wright said, he became too exhausted to continue hosting his late-night BBC radio show and had to quit.

But the troubles go beyond annoyance. Last October, a dumpster fell through a road weakened by a basement renovation in Chester Row, in the heart of Chelsea, ripping a gaping 15-foot hole in the road (the neighbors are suing). Last year, too, the art dealer Charles Saatchi reportedly became so incensed with the multiyear project next to his house in Eaton Square that he hired workmen to remove his neighbors’ scaffolding, and then put his own house on the market.