Not too long ago Michael Gove would describe his once-close relationship with Boris Johnson as being in the “deep freeze.” Such froideur was inevitable, given the way Gove had torpedoed his chum’s bid to replace David Cameron as Tory party leader and prime minister. You’ll recall that fine June day in 2016 when Johnson was poised to launch his campaign for the top job – the room was booked, the acolytes assembled – only to ditch the plan once Gove, his fellow traveller just a few days earlier on the £350m Vote Leave battlebus, announced that he had “come, reluctantly, to the conclusion that Boris cannot provide the leadership or build the team for the task ahead”.

Most friendships don’t get over a blow like that. Gove hadn’t stabbed Johnson in the back, Tory MPs agreed: he had stabbed him in the front. With next to no warning, Gove went from manager of the Boris campaign to its destroyer. Ordinarily, an act of betrayal so complete would see all ties severed for ever, the relationship dumped in a shallow grave. Putting it in a “deep freeze” represented an act of leniency.

Facebook Twitter Pinterest Johnson and Gove’s Brexit Battlebus. Photograph: Jack Taylor/Getty Images

Well, now the duo have reached for the microwave and set it on full-power defrost. Apparently, the former journalists shared a bottle of merlot together in September and decided to write a joint bylined letter to the prime minister, urging her to stand firm on Brexit and to allow no backsliding from those not demonstrating “sufficient energy” for the task.

The letter seems to be a barely coded attack on the pro-remain chancellor, Philip Hammond, and the timing of its emergence surely no coincidence: Hammond delivers his budget next week. But what makes it so striking is its joint authorship, by two men you’d have thought would never speak to each other again.

Is Johnson blessed with some saintly spirit of forgiveness? Has Gove made the most grovelling apology in political history? Of what extraordinary bones and ligaments are the friendships of politicians constructed that they can heal so easily?

The answer, surely, lies in politics. These two are now true believers in Brexit – even if, in Johnson’s case, it’s not obvious that he always was – and they can see the current risk to the project. With warning bells from business and others going off daily, they fear delay, dilution or even an indefinite postponement in the name of “transition.” The longer the process goes on, the more its flaws will be revealed. As the lead campaigners for Brexit, they need it to happen and to succeed – otherwise they will be forever associated with its failure.

This also explains why they can get away with issuing written demarches to the prime minister: since they were the public faces of Leave, in a way that Liam Fox or David Davis were not, their presence in the cabinet vouches for Theresa May’s commitment to Brexit. If she sacked them, the Brexiters would surely turn on her. So Gove and Johnson are immune, which is why Nicky Morgan suggests they are part of a “government within the government”.

It’s too soon to suggest they’re back on manoeuvers, readying another leadership bid. But still, it seems incredible that they’re once again sipping merlot together just 17 months after the great rupture. Incredible to you and me, certainly. But time moves differently for politicians. As one MP told me yesterday: “17 months is a really long time in politics.”