The brick villa — one of three identical homes built on Boltons Place between 2004 and 2006 — also has nine bathrooms, a master suite taking up a whole floor, a glass lift and a vast basement, with a swimming pool and cinema.

The purchaser will have faced a £7.6 million stamp duty bill — enough to pay 330 nurses’ salaries for a year.

Most central London sales over £20 million are either new apartments in complexes such as One Hyde Park, or 18th or 19th-century houses.

Property consultant Simon Barnes, said: “In prime central London, 99 per cent of these houses are listed or in a conservation area so you can’t just rip one down and rebuild it.”

Imposing: the swimming pool in the basement of the Boltons Place property


 

Land Registry documents show the buyer is Bermuda-registered company Mount Ltd — almost certainly a vehicle for a wealthy foreign owner — which paid £51.17 million in December.

As well as stamp duty, there will be a yearly charge of £218,000 under the Government’s Annual Tax on Enveloped Dwellings, payable by companies that own UK residential property.

Another reception room with a mini grand piano


 

The BT Earls Court telephone exchange site was bought by developers Stephen West, Paul Daniel and Giles Mackay for £13 million in 2001. They accepted a tender from contractors Walter Lilly Co to build the three houses for £15.3 million.

The exterior of the Chelsea mansion Picture: Glenn Copus


 

But the relationship between Mr Mackay — who went on to live in another of the three houses — and the builders broke down with the dispute ending up in the High Court in 2012.

Mr Mackay’s behaviour was described as “bullying and aggressive” by the judge, who ruled in favour of Walter Lilly after it claimed damages for sums wrongly deducted for alleged defects, loss and expense related to delay and outstanding unpaid value of works.

Knight Frank’s Knightsbridge office is thought to be behind the recent sale. A spokesperson confirmed it was the agent, but would not comment further.