What accounts for this reluctance to run with stories that involve the highest circulation UK paper, the world’s biggest media corporation and a key aide to the possible next prime minister? First, newspapers prefer to ignore each other’s exclusives if they can. Second, they observe the rules of “mutually assured destruction”: like nuclear powers, they don’t attack the enemy for fear of retaliation. Indeed, News International and the Telegraph agreed a sort of test ban treaty in 2007 when the latter’s owners, the Barclays, withdrew a libel claim against the Times. Third, if Coulson becomes Cameron’s press aide in Downing Street, he will become a vital source of political information. Above all, journalists prefer to keep the plumbing of their trade – the unglamorous details of how they obtain information – out of public scrutiny.