Did you march for a second, “people’s” referendum in the hope of fending off Brexit? Are you banking on a fresh slew of ministerial resignations and the new political balance in the Johnson family to clinch the argument? And might you then be expecting a civilised, fact-based campaign to reverse the result of June 2016?

Well, I hate to disappoint you. But even in the unlikely event that the prime minister executes a U-turn on a new referendum (or someone does it for her), that civilised, fact-based campaign is not going to happen. How do I know? Because I spent some time this weekend with the Bruges Group, at its conference “Brexit or Bust” – and if you thought the Brexiteers of middle England were going to roll over quietly and accept either a new vote or a different majority, you are grievously mistaken. To a man and woman they are livid, even in the anticipation.

Now the members of the Bruges Group – founded in February 1989 – see themselves, rightly or wrongly, as the heirs of late-period Thatcherism, and take their name from the speech, widely interpreted as Eurosceptic, that she had given the previous September. Their sacred text is this well-known passage: “We have not successfully rolled back the frontiers of the state in Britain, only to see them reimposed at a European level with a European super-state exercising a new dominance from Brussels”, which members can (and do) recite verbatim at the slightest prompting.

But it is not just, or even mainly, a second referendum they want to stop. It is the document now known as the Chequers plan (which they see as continuing the UK’s membership of the single market in perpetuity) and the Northern Ireland “backstop” (which they see as a manufactured pretext for remaining in a customs union) – these are the more insidious enemies.

Nor, alas, can they be accused of ignorance. Many attendees showed a fine grasp of the small print, which they could quote (to boos, hissing or applause, as required). Some wielded the argument that future growth will be concentrated in the wider world, not the shrinking economies of the European Union (minus the UK). And they are not completely wrong to see the concept of “full alignment” as limiting the UK’s freedom to go it alone. Isn’t that, after all, part of what commends it to some remainers as the least bad option?

But it was less any command of detail that struck me, or the themes, or the sometimes Ukippy tinge, than the tone of the gathering and how far these Brexiteers are united and fired up in their fury towards anything less than “Brexit means Brexit” – “Just get on and do it!” they shouted. And then the extent to which they see themselves once again (as they did pre-referendum) as right-minded rebels challenging an all-powerful establishment, which is now held to include Theresa May (boo, hiss); Commons Speaker John Bercow (loud barracking); civil servants (cries of “traitors”), and, oh yes, the media (especially loud boos).

News halfway through the afternoon that Facebook had blocked the livestream for, it was said, “breaching community standards” was met with more jeering and indignation, along with calls of “shame, shame”. Then again, what could one expect from “the establishment”? When one speaker asserted that tariffs would hurt the EU far more than the UK, the delighted audience response was “hooray!”.

At the centre of the opprobrium, though, was May, who has become a particular hate figure as sponsor, if not author – that role is allotted to Oliver Robbins, aka “Sir Humphrey” – of the diabolical Chequers plan. “If we have to chuck Chequers, we have to chuck the prime minister” was an ambition greeted with ecstatic cheers. The cry “Deceit, deceit” went up in response to the suggestion that “May-ites” were already plotting when May became prime minister; a remainer, deep down, her whole purpose from the start, it was claimed, had been “to sabotage” Brexit. More calls of “traitor”, before someone warned that Chequers could cost the Conservatives their majority. “Serve them right,” came the collective reply.

All this might, of course, simply reflect the raucous camaraderie of a particular group of Brexiteers enjoying a welcome away-day among friends. At best, it might be a last defiant shout of “down with the traitors” before the necessity of accepting a “deal” sinks in. But that is not how it felt on Saturday afternoon. Rather, it seemed that the passions which forced the EU referendum remain defiantly alive, and that at least this strand of Brexiteer will not go down without another, possibly bloody, fight. The UK’s war about Europe is not over yet.

• Mary Dejevsky is a writer and broadcaster