While the Hard Left may have many flaws, it has never been guilty of neglecting the importance of procedure. Imbued with that proper appreciation of the importance of controlling the organisation, rather than just the leadership, of the Labour Party, Momentum’s long march through the institutions of the Opposition continues at its steady, unrelenting pace.

This week it was the turn of the National Executive Committee to be absorbed by the collective. A slate led by none other than Momentum’s own boss, Jon Lansman, swept all before it (in the process helping Eddie Izzard to maintain his perfect record of losing at everything).

That victory reveals a few things about the state of play in the Labour Party:

First, that control of the leadership is not in itself enough to do everything the Corbynites might want.

Without control of the NEC, things like candidate selection rules and disciplinary proceedings were out of Momentum’s grasp, much to their frustration. But they aren’t any more.

Second, that we therefore still haven’t seen the full extent of what the clique running Labour might do if they have a free hand.

While they have cowed their internal opponents, sometimes with pretty vicious tactics, Corbynites often point to the lack of a mass purge as evidence that their controlling purism has been overstated. But the reality is that their control of the Party’s machine is still incomplete – both due to a lack of full control and out of a pragmatic desire to win fully before making a move, they haven’t yet had complete freedom of action.

Third, that the voices who want a purge are growing bolder and more strident with every internal victory. The Paul Masons of the world may not be as canny as Lansman and co, but they still matter in self-described “movement” politics. And they aren’t shy about what they now want: mandatory reselections as a starting point, “hanging over” every MP to ensure they do as they are told. Such voices aren’t in power themselves, but they wield a lot of influence in the Corbynite world.

Fourth, that there’s a danger those demands could take in a life of their own. So far, Momentum’s leadership has managed to win the argument that it isn’t yet time to act. Their authority is quite strong, and is bolstered by association with the Dear Leader. But it isn’t guaranteed they can maintain control forever – if an MP does something which is seen as so disruptive and anti-Corbyn as to gain a head of steam of online demands for deselection, the “movement” could move of its own volition, regardless of how much its leaders urge patience.

Fifth, Lansman and his colleagues have good reason to bide their time.

Momentum is quite big, and very influential, but its leaders have ambitions for it to develop much further. It has a mass of supporters, but is engaged in an intensive campaign to convert them into fully paid-up and engaged members, which will boost its coffers and its campaigning clout. Those conversions are reportedly running at 1,000 a month but the membership is still smaller than its potential base. The Momentum NEC slate pulled in over 60,000 votes, well above the current Momentum membership total.

All in all, this week’s victory is a big step on Momentum’s path to full control of Labour, but it is not the end of their ambitions. They could become richer, bigger and more powerful by far – if they can keep control of the forces they are trying to harness.