How the former US embassy became an opulent Mayfair hotel

The building is the Chancery Rosewood hotel, formerly the US embassy in London, a building designed in the 1950s by the Finnish-American architect Eero Saarinen (1910-61), now renovated and extended by the British architect David Chipperfield, with interiors by the French designer Joseph Dirand. It is, due to the insistence of the British planning system on (usually) doing right by listed buildings, a work of care, craft and expense, to a degree rarely seen in wholly new constructions.

On a perfect September day, surrounded by the superabundant foliage of the plane trees of Grosvenor Square, the hotel is a splendid gleaming thing, with sunlight catching the gold-anodised aluminium of its window mullions, and shadows forming in the projections and recessions of its stonework. The defensive ramparts and barriers erected over the years against protest and terrorism have been removed, which makes for less forbidding spaces around its perimeter.

At the same time, the project is an alliance of things that nobody quite wanted, going back to its original conception. Saarinen is best remembered for the freedom of his imagination, as seen in the soaring curves of his terminal for Trans World Airlines at JKF airport in New York. In London, restrained perhaps by the gravity of the commission and the historic dignity of the surroundings, he designed a building that hovers between heft and play, with heavy rectangles of stone set in a jiggered chessboard pattern and staccato rhythms of little stone fins set in the spaces between them.

Saarinen’s design had aspirations to represent America as a benign and welcoming superpower that were thwarted by its progressive fortification over the decades. For many Britons it became the unfriendly block outside which you had to queue for your visas. Meanwhile, its well-heeled neighbours became increasingly unsettled by having such a target in their midst. One, a Russian countess, threatened to go on hunger strike.

Eventually the Americans decided to move their embassy to a more secure location in Battersea, south London, and their former building was bought by the sovereign wealth fund of Qatar. It had been listed as a work of historic and architectural interest by the Department for Culture, Media and Sport in 2009, which might not have happened if Saarinen hadn’t been acclaimed for other projects. As it is, it was hard to ignore the only British work by an acknowledged master. Although they will have liked the prestige of its former use, I doubt that the new Qatari owners would have been all that interested in a mannered example of mid-century modernism. What they did know is that they wanted considerably more space than the old building offered (it being apparently too difficult to make money out of a Mayfair hotel otherwise), so it had to be expanded. An 18-metre-deep basement was added, containing among other things a spa, swimming pool and London’s second largest ballroom, and an extra two floors on top.

The listing meant that this expansion – a near-doubling of the original floor area – had to happen as imperceptibly as possible, so much of the art of Chipperfield and his practice went into designing an additional storey that blended happily with the existing building. On top of that is a rooftop pavilion that includes the Eagle Bar, open to the general public, placed behind that metal bird. At the same time, much of the interior structure was hollowed out and rebuilt behind the carefully retained facades. Considerable skill went into such things as matching new window frames with the old.

A first-floor reception room that was the most impressive of Saarinen’s interiors has been cleared of the later partitions that had subdivided it, and an atrium installed above it. New canopies in gold-coloured anodised aluminium, which make the entrances more conspicuous and welcoming than before, are in an informed reinterpretation of his style. The aim is not to make contrasts of old and new, but a hybrid of both.

All this is exceptionally well done. Yet the virtues of this renovation are also at odds with the values of an international luxury hotel, its construction cost a well-kept secret, where prices for its 144 suites start at £1,400 per night. The hotel wants exclusivity where Chipperfield hopes for openness, and excess where he aims for restraint. Once inside, where Dirand’s design takes over, you find that quarries have been emptied and groves felled to create a slew of marbles and hardwoods and coral-tinged chandeliers, a carnival of extraction that puts the gross into Grosvenor Square.

Meanwhile, the paranoia of the building’s former use has not wholly left. An early one-star review describes an atmosphere of control like “the world’s most secure prison”, and a pregnant woman tells how she was moved on from sitting on a step close to where that Ferrari was so nonchalantly allowed to park. You might then wonder if all that scrupulous effort was worth it. But if Saarinen had never designed his compromised but still intriguing building, and if it had not been listed, and if Chipperfield and his practice had not worked their careful magic, this spot would be poorer for it.

Photographs by Simon Menges