An image that remains lodged in the brain from more than twenty years ago is that of Roy Keane, coming through the gates outside his home in the Manchester suburb of Hale and striding towards a woodland area with his dog, Triggs. Gladiatorial defiance. The television pictures required no words. Those scenes came to mind last week when television news bulletins featured contrasting images of a less athletic man, dressed in training gear, accompanied by a small family dog, jogging past a cameraman. The character in the BBC footage was one Boris Johnson. He will be 59 on Monday. True…