Unfortunately the Border Force isn’t the only organisation under Mrs May’s control that is manifestly unfit for purpose. Recent years have seen a cavalcade of Home Office decisions about visas and deportations that suggest a department with a bizarre sense of the national interest.

The most infamous was the refusal of visas to Afghan interpreters who served with the British forces in Afghanistan - as Lord Guthrie said, a national shame.

Mrs May has kept so quiet about this and other scandals - such as the collapse of the eBorders IT system, at cost of almost a billion pounds - that you might imagine someone else was in charge the Home Office.

[It’s not just a matter of the odd error. Yvette Cooper pointed out in 2013 that despite Coalition rhetoric, the number of people refused entry to the UK had dropped by 50 per cent, the backlog of finding failed asylum seekers had gone up and the number of illegal immigrants deported had gone down.]

The reputation for effectiveness that Mrs May nevertheless enjoys derives from a single, endlessly cited event: the occasion in 2014 when she delivered some harsh truths to a conference of the Police Federation.