W hat is Andy Burnham up to? In the week of a difficult Budget, the prime minister has chosen to shove the sensitive and divisive issue of Brexit back to the top of the political agenda. For a man whose self-proclaimed mission was to unite the country and pursue a “relentless domestic focus”, he has angered some and enraptured others with his call for an “honest discussion” about the possibility of a return to free movement of workers between the UK and the European Union.

A reset summit is due in November to finalise some modest moves on food and drink border checks, the EU energy trading system and a youth mobility scheme, unobjectionable to all but the most hardened Eurosceptics. Yet this innocuous agenda is surely going to be overshadowed by this “honest discussion” – the kind of thing a hapless marriage counsellor might advise, accidentally provoking an explosion of recrimination.…