The completion of a record purchase by a Ukrainian company buyer last week has pushed the total to £963,511,720, according to advisers to the developers. The Financial Times identified the buyer as System Capital Management, the holding company of Rinat Akhmetov, who it described as Ukraine's richest man.

Just over half the 80 apartments at One Hyde Park have now been sold, according to documents at the Land Registry. Demand for the flats has been particularly strong from India, China and the Middle East.The sales have defied predictions that the development would be left as a "white elephant" after the credit crunch.

The property sold to System Capital Management (SCM) is a penthouse made up of the top three floors of the Richard Rogers-designed building and comprises two apartments  on the eighth and ninth floors that are being knocked together, parking spaces and a wine storeage room .

At 25,000 sq ft it is about 16 times the size of a typical three-bedroom house and cost almost £5,500 per sq ft, compared with a London average of £300 to £400.

All the penthouses at One Hyde Park have been sold "shell and core" which means that millions more have to be spent to fit them out. SCM is said to have commissioned interior work to a cost of £60 million.

Details of individual flat sales have been slow to be made public because of delays at the Land Registry, according to the Candys.

The development is owned by Project Grande (Guernsey) Limited, a joint venture between Christian Candy and the Prime Minister of Qatar.

Although the One Hyde Park penthouse will be easily London's most expensive flat, the world record is thought to be held by a Monaco apartment sold last year for £200 million, and also interior designed by Candy & Candy.