David Cameron wants to go to Washington for an audience with Barack Obama. He would like to bypass Brussels. If, as seems likely, the Conservatives win the coming general election, the Tory leader will discover that the facts of foreign policy are otherwise. Britain’s relationships with the US and Europe are inescapably interdependent.

Such is the national obsession with the so-called special relationship that a visit to the White House is a must-have for a British opposition leader hoping to make it to 10 Downing Street. US presidents usually oblige – though not always helpfully. The short shrift given by Ronald Reagan to Neil Kinnock when he was challenging Margaret Thatcher back in the 1980s humiliated the then Labour leader.