A three-storey penthouse overlooking Hyde Park has been sold for £136 million ($277 million), becoming the most expensive flat bought in Britain.

An unnamed buyer, using lawyers in Ukraine, has bought two apartments in the newly opened One Hyde Park development in Knightsbridge. They have been knocked into one to create a 2300sq m penthouse with a wine cellar and access to room service at the neighbouring Mandarin Oriental hotel, documents filed last week at the Land Registry show.

The price eclipses the value of landmark properties elsewhere in the world. In Beverly Hills, the 1.5ha Hearst mansion, where John and Jacqueline Kennedy honeymooned, is on the market for US$95 million ($119 million). And in Manhattan, luxury apartments in the Plaza hotel overlooking Central Park cost a little over US$50 million.

One Hyde Park has been developed by thirtysomething brothers Nick and Christian Candy, who began their property career with a £6000 loan from their grandmother and have been involved in other luxury projects, including an aborted plan to build on the site of London's Chelsea Barracks.

Nick Candy said 45 flats in the building had sold so far for a total of £963 million - an average of £22 million each: "No one else has achieved that - not just in London, but anywhere in the world," he said.

The £136 million sale was agreed to several years ago, but has only just been documented.

For the same amount, the buyer could have bought 1564 houses in Burnley, the Lancashire town recently named as Britain's cheapest with an average property price of £87,194.

The penthouse was bought as an empty shell, and the buyer is spending £60 million fitting it out.

Neighbours include the Kazakh copper billionaire Vladimir Kim, the Prime Minister of Qatar and the Irish developer Ray Grehan. Nick Candy believes buyers are investing in London because of unrest in nations such as Egypt, Bahrain and Syria.