Leave means leave. Strip away the thoughtful, learned tone of the speech made by David Frost, Downing Street’s Brexit negotiator, in Brussels on Monday and that was the gist of it. Ahead of negotiations formally opening next month he insisted, albeit in the most diplomatic of terms, that Boris Johnson wasn’t bluffing; that last autumn the prime minister may have threatened to walk away without a deal only to cave in eventually, but this time he meant it. Whatever the price of refusing to stick to EU rules and regulations, or to accept the EU courts’ involvement in enforcing them, Johnson would pay it. The itch to be free was, Frost explained, not “a simple negotiating position which might move under pressure – it is the point of the whole project”.

We won't budge on escaping EU rules, says UK's Brexit negotiator Read more

It’s scary stuff, for anyone whose livelihood is casually tossed up in the air as a result. Yet reading between the lines of a speech that was all about the principle of freedom, not the nitty gritty of what might be done with it, the space in which Downing Street seems to imagine a deal might nonetheless be done is taking shape. The only problem is that hitting it looks like the equivalent of landing a jumbo jet in a back garden in a gale.

Boris Johson’s only real red line is that Britain must not emerge looking like a rule taker. He knows that for many longstanding Tory voters, the urge to leave stems from a libertarian irritation with what they see as the ultimate in big nanny states. Railing against Brussels comes from the same powerful but irrational stable as resistance to smoking bans, speed cameras and Greta Thunberg. This itch to be free of rules and regulations often doesn’t survive contact with reality – Nick Clegg’s former director of policy, Polly Mackenzie, once described farcical scenes inside David Cameron’s government as they struggled to find some symbolic red tape to scrap, only to realise regulation mostly exists for extremely good reasons – but unless it is scratched, Brexit won’t feel real to these voters. So at all costs, Britain cannot look like a rule taker, but that’s not necessarily the same as not being one – so there is a tiny opening for compromise.

If Britain can noisily establish its right to diverge from EU rules and regulations, then it could in theory choose not to use that right much in practice, hammering out sector-specific arrangements beneath the cover of a headline deal where the government would opt for something suspiciously like the status quo. (For example manufacturing industries keen to keep selling inside the EU would need to stick to EU safety and regulatory standards even if some sought flexibility in the process of developing new products.) Frost talked soothingly about Britain seizing a competitive advantage in regulating “new sectors” where the EU couldn’t keep up with fast-moving scientific developments, rather than ripping up existing regulation. Could Downing Street be angling not so much for an Australian or a Canadian or a hard or a soft Brexit as for what might be called a cat’s Brexit?

Anyone who has ever opened a door for a cat that is clearly asking to go out, only for the cat to stay firmly put, knows how this one works. Cats don’t want to go out in the rain and get soaked-through so much as they want the option to go out, freely and sovereignly, at any point without the indignity of squeezing through a catflap. From a cat’s perspective too, doors are an insufferable brake on their global ambitions; but once the door is open, it is the cat’s business whether it just chooses to stay in the warm most of the time.

While humans tolerate this behaviour from cats because we love them, however, it’s less clear the EU has the patience. Frost’s speech upped the ante noticeably by referring to resurgent nationalist feeling across Europe, a hint that blocking British demands for independence might have knock-on effects and that even if nobody else seeks to leave, this might not be the last populist uprising the EU faces.

But if what the prime minister really wants is freedom to diverge, in return for an understanding that neither this nor future governments will exploit that freedom excessively, then that requires a huge leap of European faith in a departing ally that has done little to earn it of late. If what Johnson really wants is for Brussels to trust him, that will take more than smooth talking.

• Gaby Hinsliff is a Guardian columnist