By Jayne McCormack
BBC News NI political correspondent
Prime Minister Rishi Sunak is visiting Stormont to mark the return of power sharing in Northern Ireland.
Mr Sunak arrived in Belfast on Sunday, a day after devolved government was restored following a two-year impasse.
He and Taoiseach (Irish PM) Leo Varadkar will hold bilateral talks later.
They will also meet Northern Ireland’s political leaders, including First Minister Michelle O’Neill and Deputy First Minister Emma Little-Pengelly.
It comes as the Northern Ireland Executive – made up of ministers who make policy and decisions – wrote to Mr Sunak calling for urgent talks on long-term funding stability to deliver public services.
Ms O’Neill, who made history in becoming Northern Ireland’s first nationalist first minister, said on Saturday that Northern Ireland’s funding model was the executive’s number one priority.
Power sharing returned after the Democratic Unionist Party (DUP) ended its boycott over post-Brexit trade rules.
The DUP agreed to re-enter the institutions after a deal was struck with Mr Sunak’s government, which included the passing of new legislation at Westminster.
Analysis: Plan A pays off – but questions will come
It may be almost 12 months later than he’d planned, but today Rishi Sunak will do his victory lap at Stormont.
The original Plan A was getting power-sharing restored last April, in time for the 25th anniversary of the Good Friday Agreement.
But in Northern Ireland things rarely seem to go to plan, and the prime minister has had to be patient, keeping other ideas in his back pocket just in case.
With the final pieces in the power-sharing puzzle now slotted into place, Plan A has paid off, meaning talk of Plan B can be filed away.
However his Irish counterpart, who spoke of Plan B just a few months ago, will also be touring Stormont’s corridors today.
Leo Varadkar is no stranger to Stormont but this will be Mr Sunak’s first visit – we can expect them both to pose for plenty of photo ops and stress the need for improving public services in Northern Ireland.
But the parties will be keen to pose questions to them about what both governments can do to help with that, as the fledgling executive finds its feet.
What was in the letter to Rishi Sunak?
The government has already pledged to provide a financial package worth £3.3bn to any newly-formed executive at Stormont.
On Sunday, Mr Sunak described the package as “a generous and fair settlement for Northern Ireland”.
However, in the letter to the prime minister, the executive said the additional funding “will only serve to provide a short-term solution to the pressing issues we now face”.
Ms O’Neill said that how Northern Ireland is funded needs to change, adding she would be “strongly pressing that point” with Mr Sunak.
Deputy First Minister Emma Little-Pengelly, who jointly leads the executive with the first minister despite their different titles, added that they will be seeking to ensure the government “provides sufficient funding in a package to fulfil its promises on public sector pay”.
The letter calls for a new funding model that offers “long-term sustainability”, adding that will only happen “through joint working and delivery from both your government and the executive”.
Sir Jeffrey Donaldson, the DUP leader who does not sit as an MLA because he holds an MP seat at Westminster, said on Monday morning that he would be speaking to the prime minister about Northern Ireland’s public finances.
He said he would be “unapologetic” in those discussions.
“Northern Ireland is funded below the level of need,” Sir Jeffrey said.
“We need the government to go a bit further so our finances are in a sound position.”
However, speaking on BBC Breakfast, Secretary of State for Northern Ireland Chris Heaton-Harris said the funding package was “fair and generous”.
“The Northern Ireland Fiscal Council said in a report in May last year that it was funded correctly and this £3.3bn comes on top of that,” he said.
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.
On BBC Radio Ulster, Mr Heaton Harris questioned whether civil servants might be wrong about the figure of 127%, adding: “They have been wrong in the past.”
The secretary of state continued: “Anything that we do when it comes to public sector funding has to be based on facts and numbers rather than theory, so I am sure there will be lots of conversations based on this, but I would like to think they would be based on factual figures.
“There is a big chunk of money for public sector pay but that relies on negotiations conducted by local ministers, there’s a big chunk of money that’s new and we would like to see that spent on transformation of public services, and there’s a big chunk of money that comes from money that previously been promised by the UK govt and not spent goes into that transformation pot.”
What’s on Monday’s agenda?
Mr Sunak will travel to Parliament Buildings at Stormont, the home of the legislative assembly, to meet party leaders as well as new ministers in the restored executive.
The visit by the prime minister marks his seventh trip to Northern Ireland since entering Number 10.
His two-day trip also includes meetings with community representatives and talks with the taoiseach.
As well as going to Stormont on Monday, Downing Street said his engagements will involve speaking to a “broad range of people from across Northern Ireland including those delivering public services, those supported by them, and their families”.
How did we get here?
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.