The government has long written off the RMT, as it has the Fire Brigades Union, which severed its official links with Labour earlier this month. Neither will ministers have lost much sleep over the spectacle of the Aslef leadership turning a summer barbecue into a street brawl. But they cannot afford to be so sanguine about noises from the big four unions - Amicus, the GMB, the T&G and Unison. The RMT can make train travellers miserable. But only the big four have the clout to hurt the Labour party's finances and organisation.
That makes comments from Dave Prentis at last week's Unison conference significant. "We will not keep our heads down, gobs shut for Labour," he said. He is one of a new generation of union leaders, neither awkward squad hate figures nor Labour leadership loyalists, making common ground ahead of the election.
This platform will surface at Labour's autumn conference, over public services. Their efforts will not shake ministers from their pro-choice agenda - to be outlined again later this week by John Reid and Charles Clarke. But rows over the manifesto will cost Labour in other ways. One is Europe. For more than a decade since Jacques Delors wooed the TUC, the union movement has been a pillar of Labour pro-Europeanism. No longer. Last week big unions lined up to warn that they might back a no vote on the new European constitution. Unless union bosses are won back into the yes camp, winning a vote next year would be even more tricky than it already looks. No final bust-up is in the offing: other electoral homes for the union movement - the Greens, Respect, even the Lib Dems - look decidedly lonely against Labour's control of ministerial corridors. But as the second term draws to a close and the uncharted prospect of a third comes close, revolt is in the air.
