"We're in boom-time prices, more expensive than we've ever been in the history of mankind," Nick Candy, one of the developers of London's One Hyde Park luxury apartments, at the pinnacle of the capital's super-prime residential sector, told Reuters.
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"There is a concern over the market overheating ... Everyone thinks the main central London is doing so well, (so) the ripple effect is going throughout the UK, and some of the prices being achieved are probably unrealistic and not sustainable."
But money is still pouring in.
A source familiar with the matter said an Eastern European buyer bought a penthouse at the One Hyde Park apartment block for a record 140 million pounds.
Candy confirmed that a 16,000 square foot penthouse had been sold but declined to comment on the price or name the buyer. Developer CPC Group, which is run by his brother Christian, said the flat could be worth 160-175 million pounds when furnished.
Britain's previous record for an apartment was set three years ago by Ukrainian billionaire Rinat Akhemtov, who paid 136 million pounds for a penthouse and apartment at One Hyde Park to knock together into one property.
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There have been more than $2 billion in sales at the block, whose developer is a joint venture between CPC Group and Waterknights, the private company of Qatar's Sheikh Hamad Bin Jassim Bin Jabor Al Thani.
Candy & Candy, run by Nick Candy, were the interior designers and development managers for the project.