A year ago today, seven Labour MPs announced that they were leaving the Labour party in protest over Jeremy Corbyn’s handling of antisemitism in the party’s ranks and the Labour party’s pro-Brexit political position, to form a new political grouping, the Independent Group. They were joined over the following days by another Labour MP, Joan Ryan, and three Conservative MPs.

The group had a troubled existence, to put it mildly. They failed to sufficiently appreciate the challenges of registering as a political party which forced them into three name changes. The MPs who joined struggled to adjust to life outside a major political party. Five of the 11 ended up joining the Liberal Democrats, a party they had planned to supplant and destroy. Two stepped down at the election rather than face the voters again – all of those who did stand were defeated. In stepping down, they vacated safe Labour seats that have, for the most part, now been occupied by pukka Corbynites, swelling the parliamentary ranks of the Labour left to its largest since 1983.

A non-event in the life of British politics, distinguished only by failure? I’m not convinced. They fell short of their aims – to stop Brexit and to reconfigure British politics – but they had a significant effect on the direction of British politics.

The most important political fact at the start of 2019 was the Labour party’s strength among Remain voters. They were able to maintain their dominance among Remain voters while having an explicitly pro-Brexit policy. That meant that they were able to meet Leave voters – who have and continued to have a more negative view of Jeremy Corbyn than Remain voters do – on Brexit, while reaching out to Remainers on what you might call “small r Remain issues” like climate change, refugees’ rights and much else besides.

While the row over the Skripal poisoning damaged Jeremy Corbyn’s opinion poll rating, largely among Leavers, the Conservative divisions over Brexit, coupled with Corbyn’s strength among Remainers, meant that Corbyn entered 2019 in touching distance with the Tory party. Polls can be wrong, yes, but seeing as the polls in 2019 got the results of the local elections, the European elections, and the general election all about right we can be fairly confident that they told the correct story throughout the year.

This was the period in British politics when Corbyn most terrified Conservative MPs, and his perceived good chance of making it into Downing Street is a major reason why so many MPs were willing to put their doubts about Boris Johnson to one side. What changed? Two things – the election of Boris Johnson fixed the Conservative party’s Leave voter problem. But the other, and equally important development, was that Corbyn’s Labour developed a Remain voter problem – which meant they were no longer able to stick to a pro-Brexit positionWhy did Corbyn develop a Remain voter problem? The story of the polls is clear – it happened after the TIG breakaway. There was a shift of voters away from Labour – some to TIG, some to the Liberal Democrats and some to the Greens. Ultimately it was the Liberal Democrats, the largest pro-Remain party, who became the biggest beneficiaries of that, because TIG’s organisational failures and shortcomings meant that the Liberal Democrats were able to position themselves as the effective way of voting for TIG.

All of which forced Corbyn’s hand and meant that he had to abandon Labour’s pro-Brexit position. That had an immediate political consequence in that it ended forever any hope that the cross-party talks between Corbyn and Theresa May could end with Labour voting for a Brexit deal. It had a longer-term consequence in that it meant that Labour were from then on committed to going into the next election on an anti-Brexit platform. I’m not at this point speculating about whether Labour would have done better or worse in December with a pro-Brexit position, for two reasons. The first is that the answer is unknowable. Labour benefited in 2019 from a degree of pro-Remain tactical voting that would not have arisen had it not moved to a second referendum position and it is far from clear that the fear of Boris Johnson alone would have kept sufficient Remain voters. Equally, an election with two competing Brexit positions might have forced the substance of Johnson’s Brexit deal into the light more, which may have had painful implications for the Conservatives’ ability to win over votes and retain the support of liberal Conservative voters.

But’s it irrelevant, because the basic fact is that no Labour leader, having finished behind the Liberal Democrats in a nationwide election, would have been able to resist the internal pressure to move towards a pro-referendum position. The success of the Liberal Democrats in those May elections cannot be separated from the surge in support they enjoyed as a result of the TIG breakaway – and it’s why the events of a year ago, far from being a sideshow, were in my view one of the most crucial moments in recent British politics.