Billionaire Phones 4u founder to create 14,000-sq-ft mega-basement under Mayfair mansions

A billionaire businessperson is planning to join his two Mayfair mansions with a subterranean extension that will turn the two properties into a single luxury palace.

Plans submitted to Westminster Council by Phones 4u founder John Caudwell show that the extension would be 180 feet long and would stretch beneath both properties which have gardens that back on to each other.

Once complete, the mega-property will have 12 bedrooms; five in each of the houses and two below ground level in the planned extension.

Alongside the bedrooms, plans for the underground section include a swimming pool, sauna, games room, kitchen, media room, salon, a plant room and a car park.

The larger of the two properties already contains a ballroom, which is thought to be the largest of its kind outside of the Crown Estate.

With property prices for top homes in Mayfair at around £5,000 per sqare foot, the finished home could be worth £250m, according to the Daily Mail.

However, Caudwell could have a hard time getting the plans approved as Westminster Council is trying to put a stop to huge subterranean developments that create “iceberg” homes. Excavation works to build underground extensions for homes have more than doubled over the last five years and the building work can be very disruptive for neighbours.

Recently, Robert Davis, the Conservative deputy leader for Westminster Council, said: “It is about restricting developments akin to the decks of a nuclear submarine that are too large and cause real disruption for our residents.”