Witnessing the unexpected, often bizarre rise of Momentum has been one of the more interesting political moments of the last five years. For years political engagement had been waning, parties losing their members year on year and each election period a struggle to find enough volunteers to do the hard work of the politically dedicated which keeps the wheels of British democracy steadily turning: leafleting, door knocking, phone banks and the like.

Suddenly, with the emergence of Jeremy Corbyn as a Labour leadership candidate and later twice victor in a reprised battle for the top job, out came an army of the willing. By 2016, less than a year after the left-wing grassroots organisation emerged, Momentum had a membership of 20,000 spread across 150 active local groups. When it hosted a four-day festival of politics, culture and ideas in Liverpool to coincide with the official Labour Party conference last October, more than a quarter of those members turned out.

With each month, the power of the Momentum movement seemed to grow stronger, its ability to mobilise groups of like-minded young people unparalleled in recent years. I stumbled across Momentum picnics and cricket matches in my local park; it’s unthinkable that any mainstream party, let alone the Labour party itself in its divided state, could offer this sense of belonging and community that Momentum has created in such a short period of time.

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After Corbyn’s second landslide victory in the 2016 Labour leadership contest, despite the schisms within the official structures of the party, Momentum felt like a political force in its own right. What could it achieve? The possibilities seemed endless. Corbyn’s allies, understandably, felt emboldened; they began to bank on its presence and its power.

Now they are set to be disappointed. For what at first seemed to be a politicised army of progressives has turned out to be nothing more than a motley crew of leftists signed up to a massive Jeremy Corbyn fan club.

In recent weeks Momentum called on its thousands of members to also join up the trade union Unite, so they had the right to vote in the union’s upcoming election for general secretary. Momentum organisers wanted the group to throw its collective heft behind staunch Corbyn ally Len McCluskey, himself a controversial figure even within the union movement, who is being challenged for control of Unite by Gerard Coyne. But figures leaked to the press this week suggest that only 659 people registered as “community” members of Unite in December.

Given the union has a total membership of approximately 1.4 million members, this is hardly an entryist scandal, even if only around 15 per cent voted at the last Unite election.

The problem for Corbyn and his allies in Westminster is that Momentum really does want to do politics differently. The only thing that this coagulation of 20,000 leftist activists really agree on is that they want to create, in their own words, “a world transformed”. They won’t get down and dirty with the old-fashioned politicking required to keen McCluskey in his job. A lesson learned.

Towards the end of last year, members of the Parliamentary Labour Party were concerned that Momentum might start to influence the behaviour of the unions, and that Labour entryists coming to the party through the grassroots would be responsible for changing the nature of left-wing politics for good. That fear now looks unfounded.