The special conference (special general meeting - SGM) of the RMT transport workers' union on 30 May was an important milestone in the battle to re-establish a political voice for workers after the bleak years of Tony Blair's New Labour.
The RMT had been formally invited in March to re-affiliate to the Labour Party - from which it had been expelled in 2004 - and a two-month branch consultation took place around a Q&A document produced by party officials responding to issues raised by the union.
With the results in from the consultation, the RMT national executive committee decided, by nine votes to three, to recommend to the SGM that the union should not re-affiliate at this stage but instead continue with its current political strategy.
This, the recommended motion explained, acknowledges that Labour "has the potential to be a mass party of the working class" since Jeremy Corbyn's election to the leadership, but that the RMT can best "support, defend and develop the socialist advances that have been made" through its own independent political activity.
This was the position, argued for by the Socialist Party along with others in the broadly-backed Campaign to Defend the RMT's Political Strategy, which was agreed at the SGM.
The current political strategy also includes retaining RMT representation on the steering committee of the Trade Unionist and Socialist Coalition (TUSC), co-founded by the late Bob Crow (then RMT general secretary) with the Socialist Party and others. Since 2016 TUSC has contested local elections only against right-wing Labour candidates implementing Tory policies, making sure that the worst Blairite cutters are not left unchallenged.
The SGM decision against affiliation was not a rebuff to Jeremy Corbyn or anti-austerity policies. His occupancy of the Labour leadership is a bridgehead for the working class against the capitalists, including their Blairite agents within the party. Building from this bridgehead is the clearest route, at this point, through which workers could achieve a mass party of our own.
But the RMT was absolutely right not to unconditionally affiliate to an organisation whose structures are still largely those inherited from New Labour, which had neutered the unions' role within the party. The RMT has far greater leverage to fight for working class political representation with its current strategy than it could have achieved by surrendering its political independence and potentially handing £240,000 a year in affiliation fees (for its full membership) to the party machine.
The RMT's decision, however, should be a wake-up call to other left-led trade unions, both affiliated and unaffiliated. They must now urgently discuss with the RMT the concrete steps needed to transform Labour into a workers' party; to restore unions' collective rights and proportionate weight in candidate selection, policy formation, and the administration of the party locally and nationally.
Such measures would include mandatory reselection of MPs, with unions having the right to directly nominate candidates onto parliamentary shortlists. Local Campaign Forums, responsible for council candidate panels, should be replaced by a 'district Labour Party' structure, with directly elected union branch delegates.
The National Policy Forum, where unions hold just 16% of the votes, should be abolished and policy-making power restored to the party conference. And all expelled socialists and organisations should be readmitted, in a democratic federal arrangement, including the Socialist Party.
If the Labour Party Democracy Review, reporting in September, doesn't make such a decisive break with Blairism's organisational legacy, the left-led unions cannot just sit back.
They should insist that Jeremy Corbyn presents his own proposals directly to trade unionists, members and registered supporters like he did in the leadership contests and with a similar public campaign. Then affiliation would offer the prospect to fighting trade unionists of real collective control by workers over their political representatives.
But action is also needed now to convince militant workers that a fundamental break with Blairism has been made politically too. The SGM debate revealed how the experience of right-wing Labour-led councils implementing austerity policies is shaping workers' perception of the Labour Party and undermining Jeremy Corbyn's anti-austerity message.
The RMT has conference policy supporting local councils setting no-cuts budgets by using their reserves and borrowing powers. Yet right-wing Labour councils have now passed three sets of cuts budgets in the period since Jeremy Corbyn was elected as leader.
This was one of the issues the union raised with the Labour Party in the affiliation negotiations but the officials who drafted the party's response would not give a straight answer. But why can't an 'anti-austerity party' unequivocally say that its councillors, mayors, and assembly members will not implement austerity?
As RMT delegates gathered for their SGM the Fire Brigades Union (FBU), which had re-affiliated to Labour in November 2015 without the negotiation process that the RMT is going through, announced a nine-to-one vote for strike action in the West Midlands in a dispute with the Labour-controlled fire authority over imposed contracts. One action - why doesn't the national party suspend these alleged Labour councillors unless they back down? - would be worth a thousand 'alternatives to austerity' policy papers.
Unite's local government section also has policy for no-cuts budgets. The PCS civil servants' union, whose recent conference decided for a new consultation on political strategy, has opposed Labour-led authorities implementing cuts. They too, alongside the RMT, should be demanding concrete action from Jeremy Corbyn and shadow chancellor John McDonnell.
Even a pledge by Corbyn and McDonnell that an incoming Labour government would replenish council reserves and underwrite borrowing undertaken to avoid cuts would transform the situation in local government. How would councillors then justify continuing with austerity policies to council workers and local service users?
It would be anti-austerity politics in action and, if backed up by a mass campaign, could be a potentially terminal challenge to the May government.
The RMT SGM decision was not a rebuff to Jeremy Corbyn but it does contain a warning. The transformation of the Labour Party into New Labour was not one act but a process consolidated over years. Overturning that legacy politically and organisationally and re-establishing Labour as a workers' party will also, obviously, not be accomplished by one act.
But it will require a mass movement consciously organised to champion that goal, prepared to take on the representatives of capitalism within the labour movement at every stage. The RMT has confirmed that it is ready for the fight. Now the other left-led unions, and Jeremy Corbyn himself, must step up to the plate.