Rishi Sunak and Leo Varadkar make flying visits to Northern Ireland

They met for what the taoiseach called “a very good meeting”.

They also met political leaders separately, including First Minister Michelle O’Neill and Deputy First Minister Emma Little-Pengelly.

Mr Sunak said the new deal would protect Northern Ireland’s place in the union.

He said the return of devolved government was a cause for optimism, adding that government had “worked very hard and succeeded in protecting Northern Ireland’s place in the union”.

Mr Varadkar would not be drawn on the question of a united Ireland, instead saying that the assembly’s return showed the Good Friday Agreement was working again.

He said the new ministers were “keen to get into their briefs” and the Irish government was “here to help”.

Speaking ahead of the first meeting of the Northern Ireland Executive – the ministers which direct policy and make decisions – Ms O’Neill said “today is a good day”.

She said the parties in the executive – her party Sinn Féin; the Democratic Unionist Party (DUP); the Ulster Unionist Party (UUP); and Alliance – had “committed to working together”.

Ms Little-Pengelly echoed the first minister comments saying they were “very conscious of the big issues to tackle”.

One of the major issues being pressed by ministers is how Northern Ireland is funded.

They wrote to Mr Sunak calling for a new funding model that offers “long-term sustainability”, while Ms O’Neill has previously described it as the executive’s priority.

Mr Sunak described this package as “a generous and fair settlement for Northern Ireland”.

Meanwhile, Northern Ireland Secretary Chris Heaton-Harris told Good Morning Ulster that a Fiscal Council reported indicated Northern Ireland was properly funded and questioned figures used by ministers to call for funding changes.

He added that civil servants “have been wrong in the past”.

However, both the first and deputy first ministers said it was an issue they raised with Mr Sunak.

Mr O’Neill said incoming ministers had “in-trays as long as your arm” but proper financial arrangements had to be in place in order to deal with these.

Ms Little-Pengelly said; “We want to make sure that this executive has the right tools and sufficient resources to do what it needs to do

“We are up for that challenge and we are up for a very constructive working arrangement to try to tackle those issue together.”

In this letter, the new Executive is effectively saying the financial package announced before Christmas is almost guaranteed to lead to another budget crisis at Stormont unless it is revised.

Ministers therefore want the reopening of negotiations on significant elements, most notably the “fiscal floor”.

It is based on the devolved funding model in Wales, where it was recognised that demographic differences make it more expensive to deliver services compared to England.

The government agreed that Wales should be funded at a 115% of England’s level. In other words for every £100 per head spent on public services in England, there should be no less than £115 per head for Wales.

The government has also accepted a similar model for Northern Ireland with per head funding to be set at 124% of England’s level.

Stormont’s ministers say this is too low and has not been subject to robust independent assessment or analysis.

They believe the starting point should be 127%, with a case for it to go higher.

The difference may sounds small but over time it would represent billions of pounds of additional funding.

DUP leader Sir Jeffrey Donaldson said on Monday morning he would also be speaking to the prime minister about the issue and would be “unapologetic” in those discussions.

“Northern Ireland is funded below the level of need,” said Sir Jeffrey, who does not sit as an assembly member at Stormont because he is an MP at Westminster.

“We need the government to go a bit further so our finances are in a sound position.”

The return of power-sharing came after months of negotiations involving the government and the DUP, Northern Ireland’s largest unionist party.

It withdrew from power-sharing in February 2022 in protest at post-Brexit trade arrangements for Northern Ireland, agreed between the UK and EU.

Last week, DUP leader Sir Jeffrey Donaldson announced his party had a reached a deal with Number 10 that means no “routine” checks on goods crossing from Great Britain to Northern Ireland.

He said on this basis, and with legislation passed at Westminster to implement more changes, his party would return to government.

That decision culminated in the restoration of the power-sharing institutions on Saturday, two years to the day since the DUP walked out of the executive.