Jeremy Corbyn has one of the biggest mandates to lead a mainstream political party in modern British history. He crushed his three rivals with 60 per cent of the vote in the Labour leadership contest.
The scale of his victory has snuffed out all but the most fanciful talk of coups — for now.
Within hours of his victory, however, the MP for Islington North was being reminded by powerful party figures that he may not be given a completely free rein.
They included Tom Watson, the newly elected deputy leader and a wily connoisseur of the party’s complex structures.
Mr Watson said he favoured replacing the Trident nuclear missile system — a decision the government will make next year — despite Mr Corbyn’s hostility.
Mr Watson also said he would campaign for Britain to remain in the EU — despite his new leader’s soft euroscepticism.
In some areas, Mr Corbyn will have a free hand: for example, on his outspoken hostility to government spending cuts, which formed a crucial thread running through his campaign.
Many of the senior rightwing Labour MPs who called for responsible public finances — decried as “austerity-light” by the Corbynistas — have resigned since Saturday’s leadership result.
Mr Corbyn will also refuse to endorse David Cameron’s proposals to bomb jihadi terrorists in Syria, which is likely to prompt a split in the party.
In other areas, the new leader will soon find himself juggling radical instincts with the need to maintain party unity.
He has already demonstrated dexterity on certain issues: dropping plans to reopen coal mines, playing down his “People’s QE” idea, and hinting that he would want Britain to stay in the EU and Nato after all.
Ideological purity would lead to clashes with more than 200 of Labour’s 232 MPs who do not share many of his views — prompting dissent, even more resignations and a potential civil war.
The union leaders who keep Labour financially afloat, and who backed Mr Corbyn, reminded him on Sunday of the limits to his power.
Dave Prentis, Unison general secretary, said: “Jeremy Corbyn will have to compromise on some of the very, very clear statements he has been making. . . He will have his input, but large numbers of people will as well.”
Clive Lewis, a new MP who is close to Mr Corbyn, said people would be surprised by the new leader’s capacity to include all wings of the party in his team.
If his “hard left” postures are downgraded to “soft left”, Mr Corbyn could face pressure from radical fellow travellers: John Monks, the former leader of the Trades Union Congress, pointed out: “The danger for Jeremy will come from the left — not the right.”
One Labour MP put it succinctly: “The left always falls out with itself. It’s like the life cycle of the moth.”
Paul Richards, co-founder of Progress, the Blairite group, said Mr Corbyn was not a “feudal king” and it would not be a simple task for him to impose radical leftwing policies.
“Labour does not change immediately; policies still need to go through platforms such as the National Policy Forum,” said Mr Richards. “I think he will try to get his supporters on the national executive, the NPF, the conference arrangement committee — these obscure groups people have never heard of.”
Many senior figures are still in a state of shock about the change in direction, even if Mr Corbyn’s most radical instincts are tempered.
They believe that Labour lost the general election because it was not trusted with the public finances, and was seen as anti-business and anti-“aspiration”.
“Think of it this way,” said Ian Austin, MP for Dudley North. “In May, we offered people egg and chips. They said no — very clearly. So tomorrow we’re going to offer double egg and chips.”
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