London's elité homes: The super-prime boom

Behind London's grandest stucco-fronted façades, a new age of glass-walled, hi-tech luxury is taking shape. Chris Partridge steps into a world where house prices start at £30m

Behind the façade of a house in Eaton Square, one of London's élite addresses, an extraordinary interior is taking shape. The period rooms are being restored to their original Victorian splendour, revisiting an era when the house was owned by the Empire-building Lord Napier. But behind the historical re-creations, a new extension is being added to bring the house into the 21st century, and it is this spectacular addition that is rewriting the rule book.

Glass stairs, glass bridges and mirrored walls allow light to pass through the new extension to the rear of the house. It's a style that's becoming a signature of Finchatton, the super-high-end developer, which used a similar trick in a previous project in Hyde Park Gardens. Stepping on to the floors where you can clearly see the 10-foot drop below is alarming but undeniably thrilling.

And as if one stunning extension is not enough, a basement has been excavated under the house, garden and the mews, creating space for a swimming pool, sauna, wine cellar, cinema room and bedrooms for three staff and a security guard. Altogether, the house represents the latest evolution in the story of London's super-prime housing market, which is reaching relentlessly higher, despite any economic gloom that may stand in its way.

Alex Michelin, Finchatton's director, is confident that the house will sell without difficulty at its asking price: a cool £30m. "The super-prime market is proving very resilient to the credit crunch," Michelin says. "If our buyers want it, and it is good enough, they will buy it. We have not noticed any slowing in the market."

The world's super-rich do not need to borrow the money for a London pad. Enquire as to the identity of such buyers and a familiar cast of characters emerges: oligarchs from the former Soviet Union, oil sheikhs and, a more recent addition, businessmen from the emerging economies of India and China. Such buyers are extremely reluctant to buy outside the traditional rich areas of Belgravia, Mayfair, Knightsbridge and Kensington. Even Chelsea is a bit infra dig for the new super-rich.

The big problem for developers is the lack of suitable sites in these areas. So Michelin was very interested when the house in Eaton Square came on to the market, even though it was split into three flats and had lost its mews house.

"The house was split into three flats and the mews house had been sold off separately, so it took us 12 months before we had everything together," he says. "Because it was Grade II-listed, it was difficult to get permission for everything we wanted to do, especially installing a lift."

Security is sufficient for the most paranoid control freak – or, indeed, the most high-risk of targets. Access to the mews garage is controlled by a numberplate-recognition system, and the house can be divided into secure zones by locking interior doors by remote control. Rather creepily, all the rooms have hidden cameras, so the owner will be able to monitor the place from a BlackBerry or laptop. There is a security control room in the basement, and, of course, that bedroom for the bodyguard.

The demand for prestige houses is high, but Michelin says that the biggest demand is for flats with acres of space and no stairs. Some of the most expensive new homes in the world are the flats and penthouses at One Hyde Park, where prices exceed £5,000 per square foot. That development is being managed by Candy & Candy, the notorious young brothers (Nick, 34, and Christian, 32) who work in partnership with the architect Richard Rogers.

One of the few really large, centrally located conversion opportunities to come up in recent years is the former British Red Cross headquarters at 3-10 Grosvenor Crescent, Belgravia, now being converted into 17 huge flats by the US-based developers the BLV Realty Organization. The building consists of eight grand Victorian stuccoed houses that have been interconnected at many levels and fitted with lifts over the years, making conversion into flats possible despite the Grade II listing, which would normally prevent such alterations.

The ideal lateral apartment for a super-rich buyer will span three adjacent buildings, with nine windows, similar to the Duke of Westminster's flat in Eaton Square. Six of the flats at Grosvenor Crescent will have the coveted nine-window outlook, and one will occupy the three floors behind the grand central colonnade, with its own front door. Even lacking the view over Hyde Park, Grosvenor Crescent will certainly achieve £5,000 per square foot by the time it comes on the market later this year.

The surge of incredibly expensive new flats will do little to assuage current demand, says Rupert des Forges of Knight Frank. "Buyers at this level are fighting over not a lot. Come to my office with £10m and I couldn't offer you anything," he says.

The trend towards ever-larger apartments is in part being fuelled, ironically, by the rule, introduced by the former Mayor, Ken Livingstone, that developments of more than 10 units have to include 50 per cent affordable accommodation. Many developers are evading the need to include affordable housing by increasing the size of each home and decreasing the total number per development to nine or fewer. The result is a complete absence of new affordable housing in the super-prime area. But wandering through the hi-tech, otherworldly living spaces and plush, traditional, formal entertaining rooms of the Napier house in Eaton Square, it is easy to forget that such concerns exist at all.