Of the many subplots in the race to succeed Theresa May, one had a much speedier resolution than many in Westminster anticipated: the question of just who would win the support of the self-styled Spartans, the 28 Tory Eurosceptics who voted against the withdrawal agreement at every time of asking.

Despite the presence of candidates with much harder Brexit positions than the former foreign secretary – namely Dominic Raab and Esther McVey – almost the entire group, including its leader Steve Baker, declared for Boris Johnson. That Baker and fellow travellers like Mark Francois and Priti Patel are on board in part explains the uncompromising line Johnson has taken on no-deal as the contest has progressed.

But, as Theresa May discovered to her cost, winning the support of the European Research Group is not the same as keeping it. Much of the discussion about how the premiership of a prime minister bent on no-deal would end has focussed almost exclusively on those Tory MPs who would defy party loyalty to stop it. The reverse scenario – what no-dealers would do in the event that prime minister reneged on their promise – has received much less attention than it ought to.

The Spartans are at pains to point out that their support for Johnson is as conditional as it was for Theresa May. But how might he shore it up? One way would be to reward the group's biggest names with cabinet posts. I understand that some have made their expectation of a place at the top table clear to Team Johnson. They believe that, having so publicly lent the frontrunner credibility on the issue that matters more than any other to the Tory selectorate, they deserve repayment in kind. If it isn't forthcoming, then it will be taken as a sign that Johnson is nowhere near as serious about fulfilling his promises to the ERG as he pretended to be.

"By this time next week," one of the 28 warns ominously of the impending reshuffle, "everyone's lives will have changed irreversibly." In the event of a Johnson victory, his newfound power of patronage won't extend to pleasing every part of his fissiparous coalition. But recent history suggests that he could pay an ultimately fatal price for failing to satisfy Baker and the rest of the holdouts. Doing that won't just mean pursuing their preferred Brexit – but giving the most senior among their number the power to oversee it as cabinet ministers.