News of a breakthrough in Brussels triggered a wave of relief around Leinster House, but no one was getting carried away.

"The first thing I would say is to urge caution," Tánaiste Simon Coveney said as he took to his feet in the Dáil, before declaring the deal "a big step forward".

The tone of reaction from Government was a million Brexit years away from what it was when, to coin a phrase, "we were here before".

That was December 2017, when the Taoiseach held a press conference in Government Buildings and hailed a "significant day" for Ireland.

A deal had been clinched between the EU and then British Prime Minister, Theresa May, containing a commitment to no hard border, which Leo Vardakar said was "bulletproof". But it was one that was ultimately rejected.

This time, there was not a peep from the Irish Government when news came through of a breakthrough in Brussels at around 11am, until the Tánaiste took Leaders' Questions an hour later.

The bit that has changed from the previous deal is the backstop.

Although the Irish Government had clung to it for dear life, it is no more. But nobody has characterised this as a climbdown. This is because it is being replaced with something which the Government is arguing is far more permanent.

Instead of an insurance policy, it is a permanent policy that there will be no customs border on the island of Ireland. Regulatory and customs checks and controls would, under this deal, take place at ports at the Irish Sea and goods moving from Britain to the north.

That is with one caveat - that the north can vote itself out of the arrangement down the line. But that is something that is far more likely in theory than in practice, and for that reason, the Government can reasonably claim that the deal has met all of its key objectives: preserving the Good Friday Agreement and protecting the all island economy.

"We have always said that if we can replace the backstop with something else that does the same job on the key issues: protecting the peace process; preventing a hard order and protecting Ireland's place in the single market and customs union - then we would always look favourably on a new approach as long as the outcomes were guaranteed, and I believe they are," Minister Coveney told the Dáil.

"That is why this deal is worth supporting because it protects core Irish interests".

So while the Government can claim a significant political success in securing a deal after years of delicate diplomacy, which ultimately protects Irish interests, it just cannot - and will not - do so yet.

That is because the deal is contingent on its approval in the House of Commons - something nobody here dares take for granted.

There is "one dark cloud", as Fianna Fáil’s Dara Calleary put it, which comes in the shape of the DUP.

In the Dáil, he wanted to know (and this was before the DUP's lunchtime statement ruling it out) if the Irish Government could do anything to try to persuade the unionist party to back the deal.

The Government said it will not do so, and quickly ruled out any alterations being made that would satisfy the DUP.

"The deal is now what it is," Mr Coveney said. And while it is put to a vote in Westminster on Saturday, "the management of that is a matter for the Prime Minister and his team".

But as far as the Government is concerned, it has done all it can do. The rest is in the hands of the chaos of the Commons.