'It is hard to predict how full Brexit would play out, because this scale of multiple simultaneous renegotiations of global trade agreements is unprecedented – and no country has ever left the EU. It certainly can’t be assumed that Britain is bound to get quick and good deals because it is a large economy.'

If not, and the vote is to exit, it will be no good saying afterwards that “we didn’t understand what we were voting for” – the repeated complaint made by eurosceptics about the 1975 Referendum. By then it will be too late.