A Tory MP bobbed up at Prime Minister’s Questions recently to ask David Cameron whether he was ‘aware that 4 per cent of people believe that Elvis is still alive? That is double the number, we hear today, who think that Edward Miliband is a natural leader?’ The Tory benches tittered, Labour MPs slumped into their seats as if this was a depressingly fair point,  and the Labour leader himself tried not to look too hurt.