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Few things will be more wearisome for Theresa May than the knowledge that any given Monday her former foreign secretary can choose to use his weekly newspaper column to savage her leadership.

But so far, despite the opportunity for trouble-making that his weekly soapbox offers, Boris Johnson has chosen to stick to the same rebuke: that the Chequers proposals do not amount to a Brexit worthy of the name.

The metaphors may differ (this week it's likening the pre-scripted winners and losers of TV wrestling to what he sees as the faux negotiation and inevitable capitulation of Dominic Raab to Michele Barnier) but the message has not changed since his resignation: this is not taking back control, it's giving it up.

Indeed the headline splashed across the front of the Daily Telegraph, that the problem of Brexit "is not that we've failed, but that we have not tried", is an almost direct quote from the resignation speech he delivered in July.

The desired outcome of a "big and generous free trade deal" set out by Mr Johnson is also nothing new.

:: What is in PM's Chequers plan?

So it's not the specifics of what he is saying that will worry the prime minister, but rather the changing context in which he is saying it.

It's no secret many Tory MPs and activists don't like Chequers, but what is now becoming clear is that their opposition to it is becoming more organised and more entrenched.

Before parliament's summer break, former Brexit minister and key eurosceptic organiser Steve Baker said reports there were up to 40 MPs prepared to oppose the Chequers plan were out not by a fraction "but a factor".

The suggestion that up to 80 conservatives were ready to rebel may make reports today that there are 20 backbenchers lining up behind the "Stand Up 4 Brexit" group seem a little underwhelming.

But all that matters is whether there are enough rebels to upend Theresa May's fragile majority, and 20 would certainly be that.

Another difference is this new grouping puts names and faces to that position far more explicitly - and with senior figures like Iain Duncan Smith, Priti Patel and Owen Paterson amongst them, Downing Street will be in no doubt that they have a very public problem on their hands, one that is not likely solvable by means of the whip's thumb-screws alone.

Brexiteer rebels are also expected to intensify pressure by publishing their own plans for the way forward, likely to focus on a Canada-style free trade deal.

At the party's upcoming conference in Birmingham, all eyes will be on whether the raft of new members who have joined as part of Leave.EU's attempt to lobby for a hard Brexit from the inside will have a visible impact.

:: What Johnson would have to do to replace May

On top of all of that, add the suggestion influential pollster and strategist Sir Lynton Crosby is working on Boris Johnson's "chuck Chequers" campaign, and potentially laying the ground work for a future leadership bid, and things start to look more and more perilous for Theresa May and her insistence on sticking to her plan.

Yet there remain no signs she is preparing to cave to the Brexiteer demands. If anything, they fear she will do the opposite and cede more concessions to the EU.

So what happens next? Given the sceptical reception the Chequers proposals have received in Brussels, there are plenty of reasons to suspect they will not be accepted by the EU in any case.

But even if EU leaders chose to override Michele Barnier's concerns and accept the Chequers proposals as a workable way forward, Theresa May's chance of getting them through Parliament look highly unlikely given the noisy opposition.

Yet while the hardline Brexiteers are unanimous in their opposition to Chequers, they are far from agreed on whether toppling Theresa May should be considered a justifiable means to that end.

It is the lack of agreement on that question, rather than any Boris Johnson column, that is allowing Theresa May to continue with her Chequers plan, and her premiership.