Of the many votes at this week’s Labour conference in Brighton, one passed with very little comment: the election of a new set of officers for the party’s ruling national executive committee on Tuesday night.

That, of course, has a lot to do with the relatively tiny electorate — only NEC members could vote. But the identity of one of the new officers tells us as much about the state of Labour’s internal politics in 2019 as any floor vote: Ian Murray, its new vice-chair.

Murray is president of the Fire Brigades Union, which is much smaller and further to the left than bigger affiliates like Unite and Unison. It only reaffiliated to Labour in November 2015, having cut ties during Tony Blair’s premiership. What makes his election doubly significant is the fact that no FBU member has held a position so senior within the Labour Party before.

In one respect it reflects something we knew already: Corbynites are in control of the NEC, and are behaving accordingly. But it also illuminated one of the more interesting consequences of the left’s ascendancy. Under Corbyn’s leadership, the status and clout of smaller, more radical unions has been considerably enhanced.

The FBU have come out of this conference with one of its top brass in a senior position on the NEC. More significantly, one of its big policy motions — for a Green New Deal — passed overwhelmingly by delegates, despite opposition by the much bigger GMB.

That not only tells us just how profoundly the Labour Party has changed under Corbyn's leadership, but how the leadership has changed too. Choosing to forge ad hoc alliances with smaller unions like the FBU to circumvent bigger, richer and more powerful affiliates when need be is a sign that it is resolving internal disputes considerably more nimbly than it is often given credit for, and ultimately to its advantage.

It also gives the lie to the argument that Corbyn's ability to win those disputes starts and ends with the agreement - or lack thereof - of Len McCluskey and Unite. Instead, his credibility on the left has increased the number of union leaders whose natural instinct is to work with, rather than against, the Labour leadership. As the GMB learnt to its cost in Brighton this week, the more allies the leadership has its disposal, the easier it is to win.