Yvette Cooper treated herself to a morning off from the campaign trail last weekend. It didn’t sound very relaxing, though: she and Ed Balls, her husband, went for a dip in the chilly waters of the North Sea at Sheringham Beach. A strange fondness for cold, sharp shocks is certainly an advantage in the senior ranks of the Labour party, for whom the pain of defeat has been compounded by the spectacle of seeing tens of thousands of new supporters paying £3 to vote for the left-wing radical Jeremy Corbyn.