"Boris Johnson has admitted that he would like to be prime minister but insists 'it's not going to happen'. In a forthcoming BBC 2 documentary, the mayor of London says he thinks the job of PM is 'very, very tough'. But he will say he would like to 'have a crack' at it 'if the ball came loose from the back of a scrum'."
Johnson was head boy at Eton when Cameron was two years below him, and has never got over his feeling of superiority. But he adds -
"As a general tactic in life, it is often useful to give the slight impression that you are deliberately pretending not to know what's going on - because the reality may be that you don't know what's going on, but people won't be able to tell the difference."
In other words he really is an idiot.