If even Dominic Cummings thinks Brexit could still be a mistake – is it time to say ‘told you so’?

Often labelled the brains behind the successful Vote Leave campaign in the Brexit referendum, Dominic Cummings still managed to leave plenty of room for doubt about the success of the EU withdrawal during his interview with the BBC’s Laura Kuenssberg.

Asked whether he was sure EU withdrawal was the right thing for Britain, Cummings said: “I think anyone who says they’re sure about questions like that has got a screw loose, whether you’re on the Remain side or our side." He added: “Questions like is Brexit a good idea? No-one on Earth knows what the answer to that is.”

There are clearly many issues to deal with when it comes to something as complicated as Brexit and things will take some time to settle down, but more than five years after the vote, it is still galling to hear such a statement from a former key Boris Johnson adviser. Cummings stressed that he still believed the Brexit vote result was a “good thing” but anyone expecting a ringing endorsement would have been left disappointed.

“I think that the way in which the world has worked out since 2016 vindicates the arguments that Vote Leave made in all sorts of ways,” he said – without offering much clarification on what that actually means. “I think it’s good that Brexit happened.”

There will be plenty suggesting it would be clutching at straws to suggest that Cummings’s answers are worthy of an “I told you so” – and others who will suggest that the time for saying that was well before now. But his remarks do come at a time when government action over elements of the post-Brexit agreement with the EU leaves a lot to be desired.

Today – and not for the first time – the government is expected to warn the EU that it is prepared to unilaterally override the Brexit arrangements for Northern Ireland, the NI protocol, if a simplified agreement cannot be reached. David Frost, Britain’s Brexit chief who led a team that helped negotiate the agreement with the EU, is set to lay out the government’s position in parliament – although he made clear where we stand when addressing a parliamentary committee on Monday.

“We all know the protocol is not sustainable in the way it’s working at the moment,” Lord Frost said about the mechanism that helps prevent the need for checks on the island of Ireland’s internal border. He also said that barriers to goods moving between mainland Britain and Northern Ireland needed to be removed.

“The contradiction between the provision saying the union customs code must apply, and the provision that says that you must do your best to reduce checks at Northern Ireland ports: quite what the correct interpretation of those two things is is obviously a matter for debate,” he said. “So I think the issue is that certainly, arguably, the way the EU is allowing us to run some of these arrangements is arguably not consistent or only partly consistent with that sort of balance.”

The EU isn't totally blameless in this; neither side should have let any ambiguity into the post-Brexit agreement given the issues it would cause. The potential for moving the goal posts just shouldn’t be there – and after years of negotiation, we deserve better.

There will certainly be a significant number who read the latest headlines and raise an eyebrow. And the words “I told you so” may not be far from their lips.