Tony Blair is back in town with a speech about his new “mission”: persuading the British people that they made the wrong call in backing Brexit.

Labour’s last election winner will tell listeners that people voted “without knowledge of the true terms of Brexit”, and that as those terms “become clear”, it is the right of the people to change their mind – and the duty of pro-Europeans to do so.

It’s a measure of the febrile nature of British politics that an observation that is, to be frank, banal in the extreme is considered heretical or controversial.

Brexit might well be a success – I laid out one possible path towards that here – but it is hard to see how it will be a success that unifies half of the electorate. Blair is right, too, that just because we can see a path to making "the best of a bad job doesn't alter the fact that it isn't wise to put yourself in that position unless you have to". For those of us who still think Britain is better of in the European Union, that the promises extended to the 52 per cent cannot be reconciled with one another, let alone the 48 per cent, is reason to retain the option of a do-over if it doesn't work out.

The bulk of Labour voters who opted to leave wanted protectionism, lower immigration and higher public spending – and only one of those is likely to be forthcoming under Theresa May. Ethnic minorities who backed Brexit in Newham and Birmingham did so because they hoped for fairer and more humane visa conditions for the nations of the Commonwealth. Good luck with that.

As far as the Conservative electoral coalition is concerned, free trade with the rest of the world may please the Brexit elite in SW1, but is less likely to appeal to the agricultural seats they represent in the House of Commons - particularly if it leads to the emergence of non-tariff barriers to trade with the EU.

All of which assumes that Brexit is a success. If Britain falls out of the EU without a deal, if a hard border between Northern Ireland and the South reignites conflict in that part of the United Kingdom, and if Scotland falls out of the Union, that will have consequences for public support for Brexit, too. That Theresa May has made a series of unforced errors which have reduced British leverage only increases the risk on that score. Blair is right to say that the break-up of the United Kingdom is "back on the table" as a result of the Brexit vote.

So it’s not unreasonable or particularly remarkable that pro-Europeans should still retain hope of winning a second referendum. What is unreasonable and downright sinister is the insistence of a vocal section of the Brexit elite and their media allies that it is remarkable or undemocratic to ask for a second opinion.