You're joking. Not another one!

Could there be another Brexit referendum?

Let's get one thing straight. Another referendum would not be illegitimate. Several polls indicate that a majority of British people want a chance to vote on whatever deal May & co finally come to. The idea that it would be an affront to the will of the people as expressed on one day to ask the same electorate a different but related question two and a half years later when we all know far more is just ridiculous.

It would not be "like Ireland, being asked again and again until they get the right answer". (And the second Irish vote on the Lisbon treaty, for example, was not on exactly the same question as the first, since an extra protocol had been negotiated, ensuring that "Irish policies on tax, abortion and military neutrality would not be affected by Ireland ratifying the treaty" to address the Irish electorate's fears.)

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May has promised a "meaningful vote" in Parliament at the end of the negotiations. She has also promised that the British Parliament will get a chance to vote before the EU Parliament begins its considerations. The options in that vote are currently presented as a take it or leave it - if you don't like what we've concluded with the EU27, we'll just drop out with no deal and take the consequences (which is such a stupid idea that it should have been laughed out of court already).

Labour and others are trying to amend the EU Withdrawal Bill, currently going through the House of Lords, to make the choices more reasonable and the vote more "meaningful". "Our amendment would make it clear that, should the prime minister's deal be defeated, it must be for Parliament to say what happens next, not the executive," says Keir Starmer. Other amendments would insert an option to withdraw the Article 50 notification and remain in the EU, or to make the operation of the bill subject to a vote by the British electorate.

There are campaigns, such as the Lib Dems' "Exit from Brexit" - a vote "once a 'clear picture' emerges of the outcome of the Brexit talks", and Best for Britain's "People's Vote on Brexit", but at present Labour seem likely to whip their members in the Lords (and later their MPs, as necessary) against anything but their own amendment, which might win backing from other parties, and might leave the Commons looking around at each other some time in October or November, saying "OK, now what?".

Before the referendum, Leave campaigners seemed happy to consider a further referendum "on the terms of Brexit". Dominic Cummings, campaign director for Vote Leave, told the Economist in January 2016 that "there's a strong democratic case for it" and John Redwood wrote in 2012 (following David Davis) of a "double referendum on the EU" where two questions would be asked:

1. Do you want the UK government to negotiate a new relationship with the EU based on trade and political co-operation?"
2. "Do you want to accept the new negotiated relationship with the EU or not? Voting No means withdrawing from the EU."

Cummings was considering what leadership candidates to replace David Cameron might offer to their Tory party electorate, and Redwood's choice was Out-with-a-deal versus Out-with-no-deal, but neither they nor Davis considered a confirmatory referendum outlandish, undemocratic or illegitimate.

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But when could a "second referendum", or "the first vote on the facts" take place? The discussion above suggests that a new referendum could follow a vote in the UK parliament on a withdrawal treaty brought back from the EU summit on 22 October by a triumphant or resigned May and Davis. But would it have to wait for the EU parliament to accept or reject that treaty? You can't sensibly vote for a deal that's just been rejected by MEPs (including our own), and there's little point in voting for it if the MEPs then go on to reject it.

And what would the question be? Could there be a popular vote on May's preferred choice between her deal and no deal? Or would it have to be a multiple choice voting paper?

• Accept the withdrawal agreement
• Reject the withdrawal agreement and leave the EU with no agreed relationship and no transition (what used to be called the WTO option, or "crashing out on WTO terms", but would also mean no agreement on trade in services, security cooperation and many other things) 
• Remain in the EU

Or would Starmer's informed and empowered parliament decide the bleedin' obvious, that no deal is the worst deal of all and make it Deal v Remain? And would the Europhobic Corbyn whip (many of) his parliamentary party against that? There would certainly be opposition.

Accepting the withdrawal agreement at this point would mean proceeding to transition and negotiation of a final trade and security relationship (which might or might not all work within the agreed transition period, though the ever-optimistic David Davis tells Andrew Neil for the Spectator that "the UK and the EU will ‘get pretty substantively close’ to a free trade agreement by October").

Rejecting it and opting for Remain would see two years of legislative effort torn up, and No Deal would leave us making things up as we went along.

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Assuming that the decision to run a referendum was taken, what would have to be done? Referendums are still not a standard part of the British constitution, so a new law to define and authorise the vote would be required. I can't imagine it could be passed in an afternoon, as is theoretically possible. It would be fought tooth and nail, and arguments about advisory and binding results, and thresholds for turnout and majority, would be made with more force (and attention) than they were in 2015.

According to the stipulations of the act and the question to be asked, campaigns would have to be constituted and submitted to the electoral commission for designation. You would expect the government to be at the heart of the campaign for its deal. Would there be a freebooter campaign for No Deal? There would be a Remain organisation, and separate party or other groups to make the electoral commission's job more interesting. Much more attention would be given to funding than in 2016. And finally the campaign itself. Could a vote take place less than three months after the law was passed?

An alternative, often touted in these conversations, would be an election. But that could only do the job if parties offered distinct and opposing policies on the issue. Several small Remain parties taking on two versions of a Leave-with-a-deal-and-then... campaign would hardly be credible.

And all this would take place against the backdrop of the EU doing... what? Approving a withdrawal agreement which might be about to be thrown away? Preparing guidelines for the continuing negotiation during transition? Finalising the next multi-annual financial framework on the assumption that the UK would not be part of it? Or allowing for the possibility that we might be? Would our newly energised parliament demand the extension of the Article 50 process? Would the EU27 tell us to go away and stop wasting their time?

There are certainly polls which report public support for another vote, but there are a few others which don't. Commentators claim to identify a "just get on with it" mood, which could swell the Leave vote or the abstentions - there would certainly be people arguing that the "will of the people" can only be used once - and a "plague on all your houses" sentiment could develop, leaving us with a low turnout and an unsatisfactory result.

I still think Brexit is the wrong thing, being done badly, that it will harm us economically, reduce our status in the world, and I have a lot of sympathy for the argument that what started with democracy should end with democracy, that we should make a final, informed decision when we know what "Brexit means Brexit" means. But it's not easy. It needs turning into much more than a slogan rather quickly.