Luxury apartments in Knightsbridge have been sold off-plan for a record £4,200 per square foot, turning the development’s penthouses into Britain’s most expensive residential properties.

The unprecedented sale price achieved for some of the apartments, which have the exclusive address of One Hyde Park, puts a value of up to £84 million on the four huge penthouse suites at the top of the new scheme.

The development managers behind the scheme are Candy & Candy, the company run by Nick Candy, 34, and his brother Christian, 32.

A source involved in the scheme told The Times that “contracts had exchanged on some of the flats” for the record sum.

Even at the top end of the market for homes worth £10 million or more in Kensing-ton, Chelsea and Holland Park, residential property rarely sells for more than £3,000 per square foot.

Yet a wall of money pouring into both London’s commercial and residential property markets over the past year has pushed up the price of landmark offices in the City by about 20 per cent. Prices for smart houses in prime Central London locations are up by 46.5 per cent and even more for homes worth more than £5 million, according to research by property agency Savills.

Nick Candy said: “We know exactly who has purchased,” but he declined to divulge details of the buyers or reveal the price. “They have all signed confidentiality agreements. Demand has been off the scale from all over the world.”

One Hyde Park is still under construction, with cranes and diggers excavating the foundations over an area that used to be Bowater House, an ugly 1950s building close to the Royal Albert Hall, with views north over the Serpentine and Hyde Park.

The site was bought without planning permission from Land Securities for £150 million at the end of 2004 by an offshore-based trust company.

Candy & Candy denies that it owns the site, but were quickly hired as development managers. Candy & Candy obtained planning permission last year from Westminster council to build 86 luxury flats on the site, ranging from 1,000 sq ft to 20,000 sq ft.

The development will not be completed until 2009 and many buyers may not move in until the following year. Property experts said that buyers on such schemes can pay deposits of up to 20 per cent of the completion price, but sellers often make the deposit nonrefundable.

Yolande Barnes, head of residential research at Savills, said: “These prices are all part of the global explosion in asset prices, but London is playing in a world market, not the UK. Traditionally, Central London real estate and Manhattan went hand in hand, but over the next few years you will see London going ahead mirroring its domination as a financial centre.”

The development company on One Hyde Park is Project Grande (Guernsey) Limited.

Richard Rogers Partnership is the architect, while James Turrell is on board for exterior lighting.

The site will have underground parking for 115 cars and a link to the Mandarin Oriental, which will provide concierge service.

Providers of pads for high rollers

Nick and Christian Candy are linked to some of the most ambitious housing projects seen in London in recent years. Even before the One Hyde Park plans were drawn up, the pair hit the headlines touting what was then described as “London’s most expensive flat”, a £27 million pad that the brothers had created at a 19th-century building in Chelsea.

Their Candy & Candy is the development manager for the Middlesex Hospital after CPC, an offshore company set up by Christian Candy, bought the site for £175 million last June as part of a consortum including the Icelandic Kaupthing Bank, through its subsidiary Singer & Friedlander. The site is earmarked for a 500,000 sq ft development covering three acres, The brothers grew up in Banstead, Surrey, and attended Epsom College. Nick went into advertising while Christian became a commodities trader before they went into business designing luxury pads for high-rollers. Both brothers are now tax exiles based in Monaco.

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