Much like Boris Johnson, whose star turn on the Tory conference fringe clashed with their event, the DUP leadership mainly rehearsed their greatest hits this afternoon. Arlene Foster is against an Irish Sea border after Brexit; Jeffrey Donaldson backs a bridge across it; Sinn Fein alone are responsible for Stormont’s absence.

Foster’s demolition of the government’s planned compromise on the border (involving some new regulatory checks between Great Britain and Northern Ireland) this morning meant the DUP had already made all the news it could as far as Brexit goes by the time its leader stepped up to the lectern.

Instead, the most noteworthy comments came from Nigel Dodds, her notional deputy and the party’s leader in Westminster, where its base of power now almost exclusively lies. More often than not, his words are worth paying more attention to than Foster’s, and that rule held true today. In a punchy speech, he revealed that the DUP were signed up to the mission that is almost as important to Tory Brexiteers as chucking Chequers: Get Hammond.

Attacking the Chancellor, Dodds said: “It’s very important that the Budget should reflect optimism, that it should reflect Britain’s opportunity going forward after we leave the EU. We’ve had enough doom and gloom. This is not the time to write into the narrative that the UK is going to go downhill after we leave the European Union. This is a time to set a budget that will actually give optimism and give truth to the words that we will be a low tax country going forward. We have sent clear messages to the government on that.”

His argument is identical to that you hear from Tory Eurosceptics. In the words of Stewart Jackson, David Davis’s former chief of staff, Hammond is an “atmosphere hoover” for Leavers, unwilling to entertain what they see as Brexit’s economic potential. He is everything that they hate about the Downing Street’s approach to negotiations made flesh.

At the ERG’s conference reception last night, one minister who resigned over Chequers hit out at the Prime Minister’s “miserablist following”, singling out Hammond for criticism. “Every word that comes out of his mouth is levelled with gloom and pessimism,” they said.

In any already febrile minority parliament, this hostility to the Chancellor matters. The budget is only four weeks away. It falls between the October and November EU summits at which the Prime Minister will try and broker a withdrawal deal. Under the terms of its confidence and supply arrangement with the government, the DUP should vote for it. But today’s intervention by Dodds – who spoke to an audience that included Julian Smith, the chief whip – suggests they will make its passage uncomfortable for Hammond.

In this context, Dodds’s reference to low taxes is striking (and echoes Johnson). The chancellor is said to be planning to lift the freeze on fuel duty to help fund the NHS. The DUP’s ten MPs are opposed to any increase, as are the 13 Scottish Tories and dozens of others. His room for fiscal manoeuvre is incredibly constrained, his room for political manoeuvre even more so. Dodds has helpfully underlined this.

This offers the ERG yet more leverage. Under the terms of the Fixed Term Parliaments Act, budgets are no longer considered confidence votes. An ERG source suggested last night that they could take advantage of this in a bid to force the government to change course. “We could say: ‘That’s a nice budget you’ve got there, Chancellor,” they said. “It would be a shame if anything happened to it.’” Today, they add: “I think the budget is going to be A Lot of Fun.”

Conference, taking place as it is in a liminal space where nobody can do or say anything to change the fundamentals of the Brexit debate, was never going to be a major flashpoint for the government. The ERG leadership say they will make sure that the budget is.