A moat 30 metres (100ft) wide and rolling parkland will separate the building from the main road, protecting it from would-be bombers and removing the need for the blast barriers that so dismayed the people of Mayfair.
The State Department sought to play down the cost of security measures, noting the expense of London building work. But the price puts the London embassy above the US’s most fortified missions, including the Baghdad embassy, which cost $600 million (£390 million) but required a further $100 million of work on air conditioning, and the Islamabad embassy, still under construction, which has cost more than $850 million.
It also does not include the 17.5 per cent VAT demanded by the Treasury on all buildings in Britain and which the US has refused to pay.
Louis Susman, the US Ambassador, said: “We intend to do what’s appropriate and we are working with the Treasury on that.” He acknowleged past difficulties, pledging to be “a good neighbour in our new home” and said that the ecofriendly building would generate enough power to contribute to the national grid.
The new location will take the embassy out of the Central London congestion zone. US diplomats owe an estimated £32 million in congestion charges and fines, which they refuse to pay on the ground that they are exempt from taxes in Britain.