The sense of relief among Tories when Boris Johnson hit the campaign trail in Birmingham this week was palpable. It was obvious on the faces of party activists lined up on the stage behind him, relieved to see their leader introduce some vim and vigour to an otherwise faltering campaign launch.

The contrast with Theresa May’s campaign speeches, when accompanying activists tended to look like kidnap victims in a hostage video, could not have been clearer.

Hatred of Johnson tends to blind his many critics to the power of the man’s appeal. His capacity for cheering up supporters and potential supporters, even when they know he is peddling a piece of hokum, is perhaps the single best weapon the troubled Tories have in their depleted