Nick Clegg’s interview with the BBC yesterday, in which he declared himself “bitterly disappointed” by David Cameron’s veto of European treaty changes, was not his finest hour. No one – not even the most fanatical Liberal Democrat Europhile – has suggested that the Deputy Prime Minister “played a blinder” in his conversation with Andrew Marr. On the contrary: Mr Clegg seemed to retreat into the glib opportunism with which his party was associated before the formation of the Coalition.