It was Churchill, born to an American, who coined the phrase “special relationship” (as well as “iron curtain”) during a lecture tour of the US after the second world war. The affinity has been publicly reaffirmed by both sides ever since but proved notoriously lopsided as America surged to superpower status and Britain faded into the second rank. While most US presidents are instantly recognisable to the British, few prime ministers have left their mark across the pond.