Planning restrictions and protection orders in some of London's most exclusive neighbourhoods have meant that building expansion is quite often out of the question. So developers have hit on a new solution - develop below ground.
And the rich are lapping it up. A spokeswoman for Kensington and Fulham Borough Council told us:
"We've been inundated with planning applications for subterrainean extensions. They're becoming all the rage now. They range in scope from underground granny flats to one which proposes a 1,000 seat cinema, a recreation of a Victorian Street with three pubs, a bowling alley, an underground car park, a 10,000 seater underground football stadium, two restaurants, an olympic sized swimming pool, a casino, and a canal system with gondolas to transport users from one part of the complex to another."
This threw us a little bit. Won't this have an effect on the spaces above, we asked?
"Not really," an architect told us. "A few streets might collapse, but aside from that and a spot of disruption to the Central Line we don't foresee any problems."
Wow. More as we get it.