In an interview with the News Letter, the new Sinn Fein president said that “politics has moved on” and indicated that she is prepared for her party to return to Stormont Castle with Mrs Foster if the DUP agrees to Sinn Fein’s other conditions, which include an Irish language act.

Having toppled Stormont in January 2017, leading to a snap election, Sinn Fein’s vote soared in response to a platform where its one “red line” was that it would not return to Stormont with Mrs Foster as first minister while the inquiry was continuing.

Sign up to our daily newsletter The i newsletter cut through the noise Sign up Thanks for signing up! Sorry, there seem to be some issues. Please try again later. Submitting...

Mary Lou McDonald rejected suggestions that Sinn Fein had been asleep at the wheel while the RHI scandal was developing over several years

Initially, when asked if Arlene Foster could be first minister while the inquiry is ongoing, Mrs McDonald said clearly: “She can’t, no. There’ll be nobody in as first minister or joint first minister until we resolve the outstanding issues...”

Then, when asked if the inquiry is one of those issues, Mrs McDonald said: “Well, it clearly is because there is an inquiry under way and it clearly is because it was, if you like, the straw that broke the camel’s back and as the evidence emerges from that inquiry you see the threads not just of incompetence or sloppy practices but it raises questions around corruption or not – and I’m conscious that we have to hear some of the evidence in the autumn time.”

However, when later asked to clarify if she was saying that Mrs Foster could not be first minister while the inquiry is ongoing – even if the DUP agrees to all of Sinn Fein’s other demands – Mrs McDonald said: “No, I didn’t say that. I said that for the institutions to be re-established we need agreement on the outstanding issues and until we get to that point, frankly a debate around would Arlene be the first minister, who would be first minister is absolutely academic.

“The RHI matter is being dealt with by an inquiry. They need to conclude their work and their conclusions, I imagine, will set political imperatives in their own right. I’m not getting into that terrain.”

When it was put to the Sinn Fein president that she was no longer stating, as her party last year did in the firmest manner, that Sinn Fein would not agree to work with Mrs Foster as first minister while the inquiry was running, she said: “Well, look – we have said all along, and my preference is; our preference always was that Arlene Foster would deal with the issue of Arlene Foster and RHI and all of that.

“Politics has moved on. The world moves, you know. We’re not static.”

Mrs McDonald also denied that Sinn Fein had been asleep at the wheel in the Executive as over several years what would become the RHI scandal was developing, but said “there’s an issue about collective cabinet responsibility and people operating in silos and people being overly territorial with their departments – and that’s something that, as and when there is a new Executive, there has to be learning from that and we have to ensure whole of government approaches in terms of good governance.”