Cautious optimism gradually turned to despair at the Remain campaign’s official results party on June 23, 2016.

Activists and door-knockers mingled with government ministers over a curry buffet and warm wine, at first paying little attention to the televisions dotted around the Southbank Centre’s conference suite. While the EU referendum result looked close, the final polls had given their side — which included the leaders of all four of the U.K.’s biggest political parties — the advantage.

By 4 a.m., when Nigel Farage appeared on television to declare that “honesty” and “decency” had won the day for Brexit, just a few were left. Some were quiet and ashen-faced. Others were yelling at the television; a few had obviously been crying.

But it wasn’t a surprise for everyone. Andy Burnham, then Labour’s shadow home secretary, had broken ranks weeks before to warn that the Remain campaign was getting things wrong and in serious danger of throwing away the referendum.

Their pitch had been “too much Hampstead and not enough Hull,” he argued — contrasting the leafy north London suburb with the sort of working class northern city that ultimately propelled Leave over the victory line.

Ten years later and on the verge of becoming prime minister, one of Burnham’s first tasks if he ascends to No. 10 will now be to get Britain’s relationship with the EU back on the road. His predecessor leaves him three half-finished agreements, a postponed summit, and a discredited political strategy — all of which will need fixing.

The EU-U.K. summit, originally scheduled for July 22 in Brussels, was meant to take the EU relationship to the next level.

“Now, for sure, we need to postpone it,” European Council President António Costa told reporters on Monday after Keir Starmer announced his resignation. “But we are reassessing the opportunity of this new summit. My wish is that his successor could give continuity on this good path to reset our relationship with the United Kingdom.”

Mr. Rules

In the wake of the referendum, the political rulebook of British politics was hastily rewritten. And over the next few years, some would learn the rules faster than others. Theresa May, Jeremy Corbyn and Jo Swinson — the leaders of the Conservatives, Labour and the Liberal Democrats, respectively — all ended up losing their jobs thanks to Brexit-related miscalculations.

Determined not to go the same way, no politician pored over the new rules harder than Keir Starmer.

When he became opposition leader four years after the referendum, Starmer made two bets.

The first was that he would need to build a coalition of Leave and Remain voters to oust the Conservatives when the 2024 election came around.

The second was that he could secure the votes of Leavers by promising to “make Brexit work” — and drawing tight red lines around his EU policy.

He turned out to be wrong on both counts.

Starmer pledged no return to the bloc, its single market, its customs union, or freedom of movement. For years in opposition, Labour seemed to strain every sinew to avoid antagonizing Brexit’s support base.

But Starmer’s red lines failed to win over many Leave voters at all: 85 percent of those who would eventually back the party in 2024 wanted to rejoin the EU outright, according to the British Social Attitudes Survey, a regular comprehensive academic survey of public opinion. Labour’s coalition was if anything more pro-EU than when Starmer took over from Corbyn.

The Labour leader was also wrong about needing to win over Brexit supporters to reach Downing Street in the first place. The Tories, who had governed for 14 years straight, had imploded — and Labour was returned with a vast parliamentary majority of 160 seats.

Keir Starmer speaks to the media on July 5, 2024 as he enters 10 Downing Street following Labour’s landslide election victory. | Christopher Furlong/Getty Images

“Labour’s stance on Brexit reflects a belief that, to win the 2024 election, the party would need to reconnect in particular with those of its former supporters who voted Leave in 2016 and went on to back Boris Johnson in 2019,” the authors of the study, including veteran psephologist John Curtice wrote. “In practice, however, Labour’s support came overwhelmingly from those who say they would vote to rejoin the EU.”

Curtice, who spent the evening of the 2016 referendum crunching the numbers for the BBC, told POLITICO he had realized the pro-Brexit campaign was on course to win after Sunderland, a Labour heartland, declared for Leave. In 2024, Starmer’s Labour won every parliamentary seat in the city.

Going for growth

Given the scale of Labour’s 2024 victory, it’s unlikely that this technicality bothered the new prime minister at the time. But it would have enduring practical consequences for his government.

Despite serving no discernible political purpose, the red lines on single market and customs union membership have effectively bound Starmer to the basic framework of Boris Johnson’s Brexit settlement — one which economists now estimate has cost the U.K. six to eight percent of GDP per head by 2025.

For a government telling everyone who would listen that it wanted to bring back growth to the British economy, that was a problem.

In office, Starmer began negotiating a piecemeal set of agreements with the EU as part of a “reset” in relations. An agrifood deal, an emissions trading agreement, and a youth mobility scheme made up the first round of talks.

But by the government’s own estimate, these agreements would contribute something in the region of 0.3 percent of GDP over 15 years — far from a serious effort to unpick the damage done. Under Starmer’s “reset,” Britain’s relationship with the EU would remain based on a relatively standard free trade agreement — little more integrated with its largest trading partner than Canada or South Korea thousands of miles away.

“We used to call this a hard Brexit,” one EU official remarked to POLITICO, noting that being outside the single market and customs union was until quite recently considered a rather extreme version of leaving the bloc. “That’s what the red lines imply.”

So far, those self-imposed political limits have held. The question for Burnham, if he wins the Labour leadership, is whether or not they will see out 2026.

Virtually 10 years to the day after the referendum result ruined the party at the Southbank Centre, Starmer would be standing on the steps of Downing Street tearfully announcing his own resignation.

The occasion’s soundtrack was the EU anthem Ode to Joy — blasted at full volume over his speech from speakers set up by particularly persistent anti-Brexit protesters.

Starmer’s resignation had nothing to do with Britain’s relationship with the EU. But the inescapable background music of British politics will be playing loud for his successor, too.

Summit postponed

The EU-U.K. summit originally scheduled for July 22 had two roles. The first was to finalize the three agreements currently under negotiation by Starmer’s government. The second was to act as a launchpad for as-yet-to-be-revealed further talks to move the British economy closer to the EU’s.

But within hours of the prime minister’s resignation, EU leaders said the summit would have to be postponed.

“The EU probably feels it is constitutionally tricky for both sides to have a new prime minister agree to negotiations that have finished a week previous under a different prime minister,” said a U.K. official, who, like others quoted in this report, was granted anonymity to speak freely about the talks.

What form the meeting might return in is unclear. Burnham’s views on how the relationship with the EU should look are hard to nail down.

Just last year, the Greater Manchester mayor told Labour members at the party’s conference that he wanted Britain to rejoin the bloc within his lifetime — though during the Makerfield by-election months later, he clarified that he has no intention of making that official policy any time soon.

Burnham pitches himself as both a champion for a hard-done-by North of England — but also proponent of the kind of pro-growth “Manchesterism” he championed as a regional mayor. On Brexit, he will face the same objective pressures as Starmer when it comes to both economics and Labour’s political coalition.

Andy Burnham, Labour MP for Makerfield, appears with Labour MPs after his swearing-in at the Houses of Parliament on June 22, 2026 in London. | Dan Kitwood/Getty Images

Allies of Nick Thomas-Symonds, the current Brexit minister, say his team held discussion with the Burnham camp ahead of the Makerfield by-election to work out his position on the EU.

They believe they are on the same page — at least on issues relating to the summit — and that the Torfaen MP would be in the running to stay in post in a Burnham government, given the relationships he has built in Brussels. This would ensure some continuity in negotiations.

The manner of Burnham’s coronation will make a careful approach easier. A clean succession means there will be no bidding war between candidates one-upping each other on EU policy to win the affections of the very pro-European Labour membership. There were early signs of this last month when rival Wes Streeting — who has since backed Burnham — put the issue on the agenda by declaring that he, too, wanted to rejoin.

“Even without a summit” right in the middle of the contest there would have been an incentive for the candidates to “outgun” each other on the EU, given “Labour’s membership are strongly pro-EU,” said Joël Reland, a research fellow at the UK in a Changing Europe think tank.

The challenge ahead

If and when Burnham decides to reschedule Starmer’s reset summit, it is likely to prove far from straightforward.

In order to unlock new negotiations, the current ones must first be resolved. While agrifood and emissions trading talks are going to plan, the proposed youth mobility scheme — designed to make it easier for young people to spend time experiencing life on both sides of the channel — has hit a deadlock.

Brussels is adamant that any arrangement must cut tuition fees for European students attending British universities — who since Brexit have been paying tens of thousands of pounds more for courses than domestic students. London notes that wasn’t part of the plan agreed last year, and says its higher education sector can’t afford it.

U.K. and EU officials both told POLITICO that without an agreement on all three files, none of the deals will be signed. Expanding talks on the U.K.’s relationship with Europe, too, would seem to fall off the agenda.

“It’s clear that they go together,” a second EU official said, adding that Brussels would not accept fees being pushed into a future round of talks. Another person, an EU diplomat, added: “I think for us it’s very important to reach a deal that doesn’t have loose ends.”

It puts the summit outcome in a perilous position — and one with echoes of the original Brexit talks, with their famous refrain that “nothing is agreed until everything is agreed.”

To underscore the uncertainty, another EU diplomat told POLITICO the two sides had until last week avoided setting a date because it could “backfire” if agreements weren’t reached in time and they turned up to the meeting empty handed.

In the event, Starmer agreed to July 22 after a chat with European Council President Costa on the sidelines of the G7 summit at Évian-les-Bains. A week later, he would be resigning. Even before the meeting was postponed, a U.K. official told POLITICO talks were “likely run until the early hours of the 22nd.”

Keir Starmer announces his resignation as U.K. prime minister and leader of the Labour Party on June 22, 2026 in London. | Henry Nicholls/AFP via Getty Images

The deadlock may present an opportunity for an incoming prime minister. British negotiators have said they would consider the question of tuition fees if Brussels is prepared, in turn, to make a major offer on the economy.

What exactly that would look like is still up in the air, one British official with a close eye on talks told POLITICO. But it could be an opportunity to take the leap on a tighter relationship with the bloc that skirts with, or perhaps even crosses, Labour’s red lines.

Burnham will also take over at a time the U.K. is fighting a rearguard action against EU protectionist measures that will hit all the bloc’s trading partners. Among these, new steel tariffs, as well as the Made in Europe provisions in the EU’s Industrial Accelerator Act, are two of the most serious threats to the U.K. The issues affect the U.K.’s politically sensitive steel and car industries — making Brussels hard to ignore for a new premier.

Breaking the rules

In some respects, the U.K.’s public opinion has moved more quickly than its politicians on the issue on Brexit. Opinion polling now consistently shows a lead for rejoining the EU outright, with YouGov’s latest survey putting rejoin at 55 percent to 34 percent opposition, the rest undecided.

This is partly down to some people changing their minds.

The same pollster found that even 23 percent of Leave voters now think the U.K. was wrong to quit the bloc. But cautious politicians privately point out that most polls ahead of the 2016 referendum showed Remain ahead too, albeit by a shrinking margin. They fear the lead for rejoin may be soft and combust on contact with a referendum campaign.

“I would gently suggest to pro-Europeans in this room, including some who have spoken before me, that attempting to go back to 2016 is the same fool’s errand as Brexiteers trying to go back to the 1950s,” Labour’s Attorney General Richard Hermer, a longtime friend of Starmer’s, told a gathering of activists in Westminster on Wednesday. “We must not pretend a return to the status quo is achievable or even desirable. Many people voted against the EU because they saw it as part of a system that failed them.”

But a decade on, it’s not the same people being asked the question. Veteran pollster Peter Kellner points out that in the decade since the referendum, around six million people have become old enough to vote, and that this younger cohort says it would vote to rejoin by five-to-one. Meanwhile, another six million from the oldest cohort that backed leaving the EU by around two-to-one are no longer with us.

“The combined impact of demographics and changed minds is to convert a 1.3 million majority for leaving the EU into an 8.1 million majority for rejoining it. Even the greatest landslide election victories have come nowhere close to this lead in the popular vote,” Kellner argues.

The Brexit rulebook of politics has served the U.K.’s politicians well since 2016. A decade since it was written, the real opportunity may belong to anyone who can find a way to break it.

Sam Blewett and Anne McElvoy contributed to this report