Grimacing as the news of David Davis’s resignation reverberated round a stunned Westminster, a senior Tory attempted to put a positive spin on the latest evidence of his party’s propensity to sabotage its own political rehabilitation. “Well,” the shadow cabinet member said. “At least politics isn’t boring.”

But the excitement generated by Mr Davis’s quixotic decision to stand down as an MP to fight a by-election is the polar opposite of the political waves that David Cameron wants to make. For all Mr Cameron’s public support for his former shadow home secretary’s “brave stand”, the Conservative leader was privately furious when Mr Davis presented him with what insiders termed a “fait accompli”. When the duo met in the leader’s office, shortly after Gordon Brown scraped home on the 42-days vote, Mr Davis “told [Mr Cameron] what he was going to do – he didn’t ask,” a friend said.

Mr Cameron’s immediate reaction was dismay, shot through with concern about how this political bomb might be defused. The timing could hardly be worse. Just as Mr Brown appeared to be on the ropes, with the Tories establishing their most convincing poll lead for more than a decade, the opposition party has handed the prime minister a golden chance to regain the political momentum. Mr Cameron will be forced to lend a
supportive presence to a by-election he does not want, fought on an issue where most voters disagree with Tory policy, most likely held during the agenda-setting past few days before parliament breaks up for the long summer holidays.

“Brown was on the back foot and we’ve lent him a helping hand,” said one disgruntled Tory MP. Another shadow cabinet member could barely disguise his anger: “David Davis is tilting at a non-existent enemy, for genuinely felt but entirely egotistical reasons . . . he’s fighting on a point of principle that is already official party policy, in a by-election head-to-head with the Monster Raving Loony Party.”

The anger was not confined to the modernisers who backed Mr Cameron against Mr Davis in the 2005 party leadership election. One rightwing MP, normally a supporter of the erstwhile shadow home secretary, told the FT: “I’m flabbergasted: is he off his head? This has to be a private agenda he’s pursuing . . . maybe he’s trying to rerun the [2005] contest.”

Senior Tories insisted the electoral damage to their party could be contained, rejecting parallels with the internecine rows over grammar schools that last summer threatened to derail the party’s Cameron-led resurgence. “This is not an ideological battle – David Davis is not walking off with a wing of the party behind him. If this all goes wrong, it will reflect on him, not the leadership,” one shadow cabinet member said.

Mr Cameron sought to limit the repercussions of what he pointedly termed Mr Davis’s “personal decision” for his party by making it clear he cannot walk straight back into the top Tory team. Dominic Grieve’s appointment as Mr Davis’s replacement is a “permanent” job, aides said.

But the online reaction from the Tory faithful suggested Mr Cameron might struggle to contain the political fallout. A poll on the Conservative website found 70 per cent wanted Mr Davis reinstated as shadow home secretary. “Words of my stupendous admiration fail me,” read one posting, while another declared: “This man should have been leader!”

The realistic prospects of Mr Davis succeeding Mr Cameron as leader may be roughly zero. But if he becomes a standard bearer for the libertarian right, using his influence among the root-and-branch, his idiosyncratic stance could re-open damaging divisions.

Shadow cabinet members dismissed this prospect on Thursday night, insisting they were “cohesive and united.” But such assertions could not mask the underlying truth of Thursdays events – the only clear beneficiary of Mr Davis’s decision is the prime minister.

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