Labour politicians normally at least make it across the Atlantic before being rebuffed. However, Emily Thornberry, the shadow foreign secretary, has had to call off a trip to the US designed to present Jeremy Corbyn’s party as a government in waiting before even boarding a plane.

Diplomatic sources suggested Ms Thornberry, an outspoken critic of President Trump, had hoped to line up a series of meetings with figures in his administration. A Whitehall source said: “It became clear pretty quickly that the White House wasn’t especially keen to meet them. Can’t think why.” In the past fortnight she has described Mr Trump as a “racist” and an “asteroid of awfulness”.

Labour has also led criticism of the decision to invite the president to Britain for