Watchers of London's property market, including estate agents, potential buyers and residential conveyancing solicitors, will be keeping a close eye on the prices achieved by the developers of the capital's most expensive flats which were put up for sale in mid-April.

The 40 super-luxury flats at One Hyde Park, in Knightsbridge, have a suggested asking price of £6,000 per sq ft, with the smallest apartments listed at £5m.

According to the agents, Savills and Knight Frank, an unnamed Middle Eastern purchaser committed £28m to buy one of the homes in a pre-launch sale. The four linked blocks are due to be completed in October.

With the combination of opulent fittings, high security and the position of the flats, adjoining Hyde Park and near to Harrods and Harvey Nichols for shopping, the developers, who include the Candy brothers known for their luxury properties, are calling it ‘the most exclusive address in the world'.

About half of the 86 apartments were sold to European and Asian buyers before marketing was put on hold during the downturn, raising a total of £765m.

Other developers and those involved in high-end sales in London will view the success of sales at the mooted prices as a way of gauging how far the property market has recovered.

If the hyped figures are achieved, they will be a residential property record not just for London but for anywhere in the world this year and almost twice the best achieved in 2009.