A new billionaires' craze for building elaborate subterranean extensions is making swiss cheese of London's poshest streets – but at what cost?
"These plans are absolutely monstrous and unnecessary," said one neighbour, the Duchess of St Albans. "It's just absolute greed. No one needs that much space. Quite apart from that, the commotion is going to be dreadful."
William Cavendish-Scott-Bentinck, the fifth Duke of Portland, took over the estate of Welbeck Abbey in north Nottinghamshire when his father died in 1854, and began an eccentric reign of excavation. He dug an extensive web of tunnels beneath the grounds, connecting a series of underground chambers and stretching up to 24km – including a passage through which he could ride his carriage all the way to the station, hidden from public gaze.
Like today's residents of Kensington Palace Gardens, the Duke also had a subterranean ballroom constructed, 50m long and 20m wide, with a ceiling painted like a giant sunset. He even installed a hydraulic lift, capable of bringing 20 guests at a time down into the hall from the worldly realms above.
Yet not once did he invite people into his home. Never was the ballroom to host a dance. He would not even speak to his staff of servants, communicating only in written form through letterboxes installed in his rooms.
As Kensington's tycoons dream of digging ever deeper, retreating behind ever more layers of private facilities, they might pause to think how empty those echoing chambers will feel.