Ed Davey owes much of his election success to Boris Johnson – and in more ways than one. The slide-loving, bungee-jumping, paddleboard-slipping Lib Dem leader has, like Johnson on his zipwire, learned how to capture media attention while evading being placed on a conventional political axis. One day he’s intoning soulfully on social care in the Commons; the next rocking up to party conference on a jet ski.