Boris Johnson can change from bonhomie to a dark fury in seconds. His normally joky demeanour flashes into a sarcastic snarl, his skin reddens and blotches, his eyes dart into an intense narrow glare and on the worst occasions his lips curl back to reveal wisps of spittle. The all-out favourite to be our next prime minister has the fiercest and most uncontrollable anger I have seen. A terrifying mood change can be triggered instantly by the slightest challenge to his entitlement or self-worth.

It was the sight of Boris Johnson in full flow that convinced me all those years ago in the 1990s, when I worked alongside him in Brussels reporting on the EU for The Daily Telegraph, that he was temperamentally unsuitable to