Into these multi-level subterranean structures owners are building anything from cinemas, swimming pools, beauty parlours, squash courts, wine cellars and servants' quarters. Some take as long as three years to complete.
As well as the noise of the digging, fleets of concrete mixers and lorries taking away the dug soil service the sites. So life for neighbours in some of London's poshest addresses has been hell.
Historian Ruth Goodman uncovers the surprising origins of the poodle's famous haircut; finds out what makes greyhounds the fastest dogs on the planet; and travels to the Guisachan Estate in the Scottish Highlands to meet hundreds of golden retrievers at the ancestral home of this popular breed.
As the Royal Borough of Kensington Council responds to angry residents and tries to regulate the number of mega-basements and the disruption they cause, this BBC film goes behind the hoardings to look inside the extraordinary structures and talk to builders, owners and irate neighbours to tell the story of the conflict that has gripped the millionaires and gold-paved streets of London's smartest postcodes.
Thanks for stopping by. We welcome your comments.