Grosvenor Square was first linked to the US in 1785 when the first US minister resided there. During WW2 the American Chancery was located on one side with Eisenhower’s headquarters opposite, and the area was dubbed ‘Little America’. When a competition was held to design a new Chancery in 1955 entrants were encouraged to ‘grasp the historical meaning of the particular environment ’.

Eero Saarinen triumphed with a design intended to respect the square’s Georgian character. Its Portland stone facade was to harmonise with the surrounding buildings as it darkened in time to match its neighbours. The sturdy rectangular form represented US democracy, punctuated by lattice-like fenestration and crowned by a 35ft gilded aluminium eagle by Theodore Roszak.

The building received a frosty reception from the architectural establishment with Reyner Banham dismissing it as ‘monumental in bulk, frilly in detail’. The predicted weathering by soot was thwarted by the 1956 Clean Air Act and the London Observer likened the gleaming edifice to ‘costume jewellery’. Saarinen himself was not uncritical, responding ‘In my own mind the building is much better than the English think – but not quite as good as I wished it to be’.