Daniel Hannan is an MEP for South-East England, and a journalist, author and broadcaster. His most recent book is What Next: How to Get the Best from Brexit.

I have been watching the dégringolade of Brexit with – if such a thing is possible – even more agony than the rest of you. It’s not just the frustration of seeing mistake after avoidable mistake being made by our side. It’s not just the tossing away of a generational opportunity to relaunch Britain as a global trader. It’s something else. You see, I had always expected, at this stage, to be one of those Leavers who could warmly back a compromise deal.

As regular readers of this column will know, I never liked the idea of a WTO Brexit. I wrote here on the day of the referendum itself that, whichever side won, it would need to accommodate the large minority which had voted the other way. I have spent two years suggesting various compromises that both sides might live with. So when the clever and amiable David Lidington urges us to back the withdrawal deal on grounds that “the 52 per cent get control of laws, money, borders + out of CFP; the 48 per cent get closer trade partnership with EU than Canada or any advanced economy + cooperation on police & security,” I really want to agree.

Liders, after all, is more or less taking the line I have been taking over the past two years. A 52-48 vote, as I kept telling anyone who’d listen, was not a mandate for a radical break, but for a phased and partial recovery of powers. When critics complained that we’d be left “half in, half out”, I’d retort that that was pretty much the way the nation had voted, and that there was no dishonour looking for a middle way.

But here’s the thing. When I suggested accepting a half-in-half-out settlement, I assumed we’d aim to keep the good half and junk the bad half. The Eurosceptic demand, down the years, had always been “common market, not common government”. That was the position of Teddy Taylor and Dick Body and, before them, of Neil Marten and Enoch Powell, of Hugh Gaitskell and Clement Attlee. It seemed a safe bet that the government would respond to the 2016 vote by seeking something along those lines. I wanted Swiss-style EFTA membership, but I was prepared for pretty much any reasonable compromise.

Yet, incredibly, Theresa May has come back with a deal that keeps the worst aspects of membership and junks the potential advantages. Instead of staying in the common market but leaving the EU’s more federal policies, we are doing the reverse. We propose to leave the common market but keep, as much as any non-member can, the obligations imposed on us by the European Arrest Warrant, the Common Foreign and Security Policy and the rest.

Instead of doing a Switzerland – leaving the Customs Union but retaining chunks of the Single Market – we shall end up staying in the Customs Union but leaving most of the Single Market. In other words, we shall prejudice our trade with the EU 27 while simultaneously making impossible trade deals with anyone else.

If you had asked three years ago whether leaving the EU while keeping the Customs Union was desirable, you’d have been laughed at by all sides. It had always clobbered Britain uniquely as the member state that did the most trade outside the EU. The idea that we might stay in it while giving up any say over it, obliging ourselves to follow all EU concessions to third countries without any incentive for those third countries to reciprocate to us, would have been too absurd to contemplate.

How have we ended up in this humiliating position? In Labour’s case, the answer is sheer opportunism. The party was anti-Customs Union until February of this year on the impeccable grounds that, as Jeremy Corbyn put it, “it is protectionist against developing countries”. It reversed its position when it scented an opportunity to win a parliamentary vote, but I still haven’t heard a single Labour MP come out with a convincing defence of the new policy. Indeed, debating some of them, I’m left wondering whether they have any grasp of what the Customs Union is. Labour now seems to be anti-Single Market but pro-Customs Union on no better grounds than that it doesn’t like the word “market” but does like the word “union”.

The Government’s position is even odder. Having promised on more than 20 occasions that Britain would leave the Customs Union, the Prime Minister now presents as a victory the fact that the backstop would keep the whole UK in that subordinate position. In fact, of course, this was the EU’s aim all along. The row over the Northern Ireland border was invented as a way to grip the UK in the tight clamp of the Customs Union, giving EU exporters preferential access to our market while simultaneously allowing Brussels negotiators to use that market as a negotiating counter to get better terms for their own countries.

The claim that the Customs Union is temporary depends on our faith in two things: the Prime Minister’s negotiating ability and the EU’s generosity. On the basis of the record of the past two years, is that a gamble you’d make? The other EU states are not hiding their glee at our surrender. Emmanuel Macron has already said that he will veto a future trade deal – that is, keep us in the Customs Union – unless we open our fishing grounds to his skippers. It takes only one country to wield a veto at that stage, so Madrid might make a similar threat over Gibraltar, Dublin over Ulster and so on. Britain would by then have handed away its £39 billion and all its leverage. Are we really supposed to believe that the EU would terminate a position that is, as Donald Trump correctly says, advantageous to the 27 but excruciating for Britain, out of sheer goodwill?

I can’t speak for every Eurosceptic, but most of us voted Leave because we wanted a freer, more democratic and more global Britain. We didn’t want to sever all our links with our European allies. We simply wanted to be free to stand aside as they pursued their goal of political amalgamation.

The deal that will come before Parliament doesn’t offer that outcome. Quite the opposite: it would lead to a Britain that is as constrained as now, but less commercially engaged. The only Leavers who might support such a deal are those Old Labour voters who want a protectionist Britain and fewer foreign workers. Yet, as far as I can tell, even they don’t like it.

Supporters of the deal are (with the exception of the brilliant but, on this occasion, mistaken Rory Stewart) not really trying to make a positive case for it. Instead, they are reduced to telling us that the alternatives are even worse and that everyone is sick of the whole business. They’re wrong. The alternatives have not been tried, and most Leavers only ever supported Brexit as a means to an end, not an end in itself. This agreement delivers an outcome worse than either staying or leaving. It has been negotiated by people who never liked what they were doing, never understood why anyone might have voted Leave (other than on anti-immigration grounds) and defined their success as coming back with something – anything – to which they could attach the label “Brexit”. They have misjudged the electorate; and they have, I think, misjudged the MPs whom that electorate returns.