David Cameron will receive a warm, and possibly rapturous, reception from Conservative MPs on Monday when he reports back to parliament on the European summit.
Barring a last-minute accident, the prime minister will say he played a leading role in drawing up the first cut in the EU's budget in its 56-year history.
As he headed out of the European council to freshen up during a break in the negotiations on Friday morning, after one of the EU's dreaded all-night sessions, No 10 was hopeful he had secured his original target.
Cameron had always aimed to secure a real-terms freeze in the EU's near-€1tn budget. The latest proposals, presented by the European council president, Herman Van Rompuy, in the early hours of Friday, called for the EU's "payment ceiling" to be cut from €942.8bn in 2007-13 to €908.4bn in 2014-2020.
The prime minister hopes to be able to go one step further and say that he has secured a cut in the budget, the first time this has happened in the history of the EU.
Nothing is ever agreed in the EU until everything is agreed. This meant that British government officials were careful not to punch the air on Friday morning, as the British ambassador to the EU's political and security committee, Julian Braithwaite, made clear. He tweeted: "UK Delegation at #EUCO buzzing. Nobody's relaxing. It ain't over 'til it's over, nothing's agreed until everything's agreed."
But if the Van Rompuy plan does hold, it is difficult to imagine better timing for the prime minister. Weeks after he was warned that he was marginalising Britain in the EU by outlining plans for a referendum by the end of 2017, Cameron has shown that Britain can shape events.
The prime minister will say that the latest summit shows the wisdom of his three fundamental calculations about the EU. These are that Britain should never underestimate its ability to be a major player in the EU. It should also not be frightened of laying down red lines that cannot be crossed, though it helps not to refer to them in that way.
Cameron's final – and most important calculation – holds that the key player in EU negotiations is the German chancellor, Angela Merkel. If she is pushed too far, Merkel will bite, as she did in December 2011 when she drew up the eurozone fiscal compact treaty outside the EU after Cameron wielded a veto.
But if she believes that Cameron's demands are reasonable, then she will work constructively with him as she did over the EU budget. This meant Cameron could afford to risk a frosty reception from the French president, François Hollande, who ducked out of a joint meeting with Merkel and Cameron, and still broker a deal.
Fuelled by an overnight supply of Haribo sweets and Nespresso coffee in the UK delegation room in the Justus Lipsius building – the red decaffeinated capsules were the only ones left over – the prime minister may think he is invincible.
But Cameron might like to bear in mind the thinking of Merkel's officials in the runup to the first budget summit in November. Berlin was quite prepared to see Cameron isolated to show Merkel's displeasure as she awaited his speech on the EU, which she feared would be unremittingly hostile. In the end, Merkel worked closely with Cameron in November for one very simple reason – she agreed with his call for restraint.
The German chancellor is keen to co-operate with Cameron at a tactical level – if she agrees with him – and at a broader strategic level to maintain the UK as an influential member of the EU as a counterweight to the protectionist France. But Merkel's support should never be taken for granted. The prime minister will therefore need to calibrate his negotiating stances with care when he embarks on the much more delicate and complex task of repatriating EU powers, as he promised in his Bloomberg speech on the EU.
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