If it wasn’t so bloody serious, you’d have to laugh at the irony of it. Back in August 2004, the then MP for Henley joined a small group of parliamentarians calling for the prime minister, Tony Blair, to be impeached. The reason, wrote Boris Johnson, was the “dishonest means of persuasion” Mr Blair had supposedly deployed in the period before the invasion of Iraq.

Nearly 14 years on, it is Mr Johnson accused of being a liar. Two weeks ago (the charge reads) he told a German interviewer that a Porton Down scientist had assured him categorically that the Russian government was responsible for the Skripal attack. But the chief executive of Porton Down, Gary Aitkenhead, interviewed this week, apparently said that his staff couldn’t