Sinn Feins Michelle ONeill speaking to Mark Carruthers on BBC politics programme The View on Thursday night

Ideologically, such a stance is extraordinary in that is essentially would mean that the successors of the Provisional IRA would voluntarily relinquish power to British ministers rather than jointly rule with the DUP over part of the island of Ireland.

Sinn Fein will not come out and say such a thing. The party will call for joint authority (knowing that is impossible under the Agreement) and will rail against the idea of Conservative ministers once again administering Northern Ireland.

But the party knows – and has over recent years been the clearest to articulate the fact – that the only alternative to power-sharing in Belfast is direct rule. The unpalatable choice for republicans is now between James Brokenshire and Arlene Foster.

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A month ago today, Michelle O’Neill said that during a meeting with the Secretary of State she had “told him that there would be no return to the status quo and no return to direct rule”. If the strength of the word “told” was deliberate, it was deliberately misleading. Sinn Fein simply does not have the ability to stop direct rule – unless it agrees to enter an Executive.

Until now, Sinn Fein’s demands for concessions before re-entering an Executive have not been couched in absolute terms. Calls for an Irish language act and gay marriage have been prominent, but not set out as red lines.

The firmest Sinn Fein demands have been vague – calls for “respect” and a vow that there would be “no return to the status quo”.

But, in her first major televised interview since taking over as Sinn Fein’s leader in Northern Ireland, Ms O’Neill told Mark Carruthers on Thursday night that Sinn Fein will not re-enter Stormont Castle with Mrs Foster while the RHI inquiry is ongoing – something which will take months, and possibly more than a year.

Unless the DUP is suddenly so desperate for power that it abandons its leader, that statement radically alters the post-election landscape.

Indeed, it is questionable as to whether there would be any point in even negotiating about forming an Executive – assuming that Sinn Fein and the DUP retain their positions as the top two parties – if that insurmountable hurdle remains.

The DUP clearly envisages a new direct rule era on the horizon. In her speech at the DUP’s campaign launch on Monday, Mrs Foster spoke of a period of “sustained and prolonged” direct rule.

In political terms, Sinn Fein’s two most vocal demands – an Irish language Act and same-sex marriage – are far more likely to be acceded to by Theresa May than by Mrs Foster. There is therefore a certain political logic to Sinn Fein seeing virtue in a period of direct rule – particularly when Mrs Foster has just re-stated that she will not make concessions such as an Irish language act.

The increasingly close DUP-Conservative relationship at Westminster may be an impediment to the Tories really aggravating the DUP and would have to be balanced by some corresponding concessions to the DUP. But even some in the DUP might be strategically content to see those two issues removed from the picture if it guarantees them five more years at the Stormont helm, heading towards Northern Ireland’s centenary in 2021.

And if the government did implement such legislation it would be a considerable goad to the DUP’s supporters, reminding them of the sorts of arguments which Ian Paisley laid before them a decade ago to justify his move into power-sharing.

But although in the short term Sinn Fein may gain political advantage from a few months of direct rule, such a scenario poses fundamental questions for republicanism.

Just a year ago, Martin McGuinness warned against direct rule, saying that it would involve an “inevitable Tory onslaught on our public services and the most vulnerable in our society”.

And just a couple of months earlier Gerry Adams had similarly warned that “British direct rule” would involve “the full weight of a Tory assault on the welfare state”.

The Sinn Fein president asked: “We should ask those in favour of the institutions collapse do they really want to let the Tories impose water charges, increase student fees, impose prescription charges, end free travel for pensioners and slash public services in the North? That would be a likely consequence if the talks had failed, or if the institutions had been suspended.”

He pledged: “Sinn Féin will not hand over the political institutions and hard-won agreements to the Tories.”

Having made clear that Stormont is now no longer sacrosanct and it may not allow the Executive to return – in the knowledge that Tory direct rule is the only alternative – Sinn Fein has performed more than a political U-turn.

Choosing a British direct rule minister over what it sees as a truculent (but Northern Irish) political leader poses ideological questions for republicans which go far deeper than whether Stormont stands or falls.