Image source, Reuters

Today represents a "huge test and a huge opportunity" for the prime minister, one think tank director tells BBC News.

There's "quite a lot at stake" in any deal with the EU, says Prof Anand Menon from UK in a Changing Europe. He cites various matters requiring future cooperation between London and Brussels - issues from the small boats crisis to electric vehicle legislation.

But "we have to wait and see" whether potential opponents of a deal secured by Prime Minister Rishi Sunak will be willing to compromise, Menon says.

He describes this as a "moment of truth" for the PM, who has so far "tended to swerve" challenges during his premiership.

Image source, UK PARLIAMENT/JESSICA TAYLOR

For the past year, the Democratic Unionist Party (DUP) has blocked the operation of devolved government at Stormont in protest over the Northern Ireland Protocol.

In June 2021, just weeks after Sir Jeffrey Donaldson took over as DUP leader, he set out seven tests which he said must be passed before his party could support any new post-Brexit arrangements for Northern Ireland.

The tests are:

• Compatibility with the Act of Union which says all parts of the UK should be on equal footing when it comes to trade
• Avoiding any diversion of trade where NI customers are forced to switch to non-GB suppliers
• No border in the Irish Sea, meaning no goods checkpoints at NI ports like Belfast and Larne
• NI citizens to have a say in any new regulations which impact them
• No new checks on goods traded between GB and NI when those goods are staying the UK
• No new regulatory barriers between GB and NI unless agreed by the NI Assembly
• Honouring the 'letter and spirit' of NI's constitutional position as set out in the 1998 Belfast/Good Friday Agreement by requiring upfront consent of any diminution in constitutional status

Read more about the DUP's tests here.

Image source, Getty Images

More now from prominent Brexiteer Jacob Rees-Mogg.

He stresses that the view of Boris Johnson, the former prime minister, will be "important" in whether or not any deal gets over the line.

Johnson is "the biggest figure in UK politics," Rees-Mogg tells GB News, "and therefore his view will be of fundamental relevance to how this debate is carried out".

Rees-Mogg acknowledges the government appears to have won "some important concessions" from the EU.

But he's critical of what he sees as an "unfortunate" failure to consult the Democratic Unionist Party (DUP) in Northern Ireland. He suggests the government is "taking a punt" on its deal being accepted by that party.

Nick Eardley
Chief political correspondent

Sceptical Tory MPs were contacted by cabinet ministers trying to sell the deal over the weekend.

They say they were promised they would not be "bounced" into a quick decision.

Senior Brexiteers say they expect a vote on the deal - but No 10 has not confirmed this.

Image source, PA Media

Not necessarily. Legally, the government only has to offer MPs a vote on any changes in limited circumstances. But it will face pressure to give backbenchers a say.

Asked at Prime Minister’s Questions last week whether MPs would get a vote on any deal, the prime minister said Parliament would be able to "express its view".

Afterwards, his official spokesman was tight-lipped on the question, saying: "We are not going to get ahead of ourselves... We would be getting into hypotheticals to talk about a vote."

Speaking to the BBC’s Sunday with Laura Kuenssberg, Deputy Prime Minister Dominic Raab also avoided saying explicitly that MPs would vote on the new deal, only that Parliament would be able to "express itself".

Labour has said it would back the government in a vote - something reiterated by Rachel Reeves this morning. However, the prime minister could still face a rebellion from Brexit-supporting Conservative MPs.

Unionist parties support Northern Ireland being part of the UK. They argue that an effective border across the Irish Sea(represented by the current Northern Ireland Protocol) undermines that status.

Northern Ireland's largest unionist party, the DUP, has stayed out of government since February 2022 in protest over the protocol and is refusing to re-enter power-sharing unless the arrangement is significantly changed.

That means the Northern Ireland Assembly has been stymied, as it can only function with the co-operation of the largest nationalist party and largest unionist party.

Despite concerns among unionist parties, many members of the Northern Ireland Assembly are in favour of the protocol in some form remaining in place, but have said improvements are needed to ease its implementation.

We're now able to report that PM Rishi Sunak and EU Commission President Ursula von der Leyen will meet at 12pm in Windsor.

The pair are meeting to discuss "complex challenges" around the protocol.

Jayne McCormack
Northern Ireland political correspondent

Image source, Charles McQuillan/Getty Images

The DUP knows the spotlight is going to be firmly on them today. They, along with a lot of others, have not seen the full text of the proposed Northern Ireland Protocol deal.

When Rishi Sunak recently visited Northern Ireland and spent a lot of time with the DUP, the party saw bits and pieces of the proposals.

Clearly at that point, it wasn't enough for them to turn around and say "no".

But I was told by somebody within the DUP last week that they were gearing up to have their legal minds within the party ready to go through this thing with a fine tooth comb when it is published.

So, we're not going to get any big pronouncements or verdict from them today, that's not their way.

They'll probably issue something very short to say they are going to reserve judgement.

Often there is talk of this split within the DUP where some of its MPs tend to be typically more hard-line, compared to some of its Stormont assembly members who haven't been able to do their full job for more than a year.

So before DUP leader Sir Jeffrey Donaldson comes to any final verdict on this deal, he is going to have to try to bring together different factions of his own party.

The Northern Ireland Protocol came into force at the start of 2021. But by March of that year, the EU had begun legal action for alleged breaches.

February 2022 saw Northern Ireland's DUP - which has long campaigned against the protocol - pull out of power-sharing government at Stormont.

In June last year, the UK government outlined a bill aimed at unilaterally changing trade, tax and governance arrangements in the Northern Ireland Protocol. This angered the EU, which restarted its legal action, having earlier paused this.

Brussels said it was not prepared to renegotiate the protocol, but offered to work on how the rules were applied, including:

• Reducing customs and checks on goods
• Reducing the amount of paperwork
• Relaxing rules so chilled meats could still be sent across the Irish Sea

Technical negotiations between the UK and the EU restarted in October 2022, external.

In January, the two sides reached agreement on sharing data on trade. This was seen as paving a way for a broader deal.

The past couple of weeks have seen a flurry of activity, with PM Rishi Sunak visiting Belfast - to meet politicians in Northern Ireland - and then Germany, where he met European Commission President Ursula von der Leyen. The two meet again today.

Jessica Parker
Reporting from Brussels

The EU wants to help Rishi Sunak get this over the line.

That may be one reason why the European Commission President Ursula von der Leyen is heading to the UK.

It makes for far better optics, for the prime minister, than if he were to do a handshake moment in Brussels.

That’s especially true if he ends up facing any accusations of having given too much ground to the EU. But don’t expect Brussels to boast too loudly about any of its negotiation “wins”.

Again, they know that wouldn’t aid Sunak in getting his own party – and Northern Ireland’s Democratic Unionist’s – on side.

But no matter what the EU says or does in the coming days, this will ultimately be a test of Rishi Sunak as a political salesman.

Image source, PA Media/Reuters

The possibility of a new deal governing the paperwork on how goods move from Great Britain to Northern Ireland comes after a weekend in which senior politicians went out of their way to suggest that every sinew was being stretched to reach an agreement.

On Saturday, Irish Prime Minister Leo Varadkar told reporters that a deal was “inching towards a conclusion”.

His comments acted to dampen down speculation that a new accord was very imminent - following reports European Commission President Ursula von der Leyen would be in the UK on Saturday to jointly announce a deal with Prime Minister Rishi Sunak.

On Saturday evening, the Sunday Times dropped its lead story - with Sunak telling the paper: "I'm here all weekend trying to get it done... We're giving it everything we've got."

By the time the Sunday morning political programmes went on air, it was the turn of Justice Secretary and Deputy Prime Minister Dominic Raab to manage expectations.

Speaking on the BBC’s Sunday with Laura Kuenssberg, Raab said: "We're on the cusp, we've made great progress, we're not there yet, but it would be a really important deal…”

But now the announcement of a new post-Brexit agreement with the EU over the flow of goods to Northern Ireland looks close, and we’ll bring every detail to you here.

Nick Eardley
Chief political correspondent

Image source, Getty Images

Cabinet ministers were deployed to sell the deal to sceptical Tory MPs last night.

They were promised they would not be bounced into a quick decision.

Although No 10 has not confirmed there will be a vote in Parliament on the deal, Brexiteers are expecting one after discussions with senior ministers.

This is an extremely important moment for Rishi Sunak's authority. He will want to keep any rebellion as small as possible.

Two things could be key here:

1. How much European law does Northern Ireland have to follow? We don't expect European Law to be "expunged" fully - as some are demanding. But if the number of rules that apply are minimal, and it's clear the European courts will only play a role in extreme circumstances, some Conservatives could be won over
2. What does the DUP do? Don't expect an answer to that tonight. But what the party says over the next few days will be key. If they don't criticise the deal explicitly, that could reduce the size of a rebellion. If they are vocally unhappy, the rebellion could grow. One Tory MP told me last night: "The bottom line is - if this doesn't result in power sharing, it's not a worthwhile agreement"

Liberal Democrats leader Sir Ed Davey says his party "will do the responsible thing" and support a deal on the Northern Ireland Protocol if the agreement has the potential to help Northern Ireland and the British economy.

"We will act responsibly in the national interest," Davey tells BBC Breakfast.

"It’s our patriotic duty to get behind a deal that helps Northern Ireland and gives some little boost – a much needed boost – to our economy and so we’ll do that, assuming when we’ve seen the deal, it does make sense."

Davey adds that Parliament should have a vote on any proposed deal and says the Conservatives have "mismanaged" protocol negotiations "for so long".

"It’s hit people and businesses in Northern Ireland, but it’s also undermined our economy and the government have got to get their act together.

"Whether the prime minister will be able to sell it to his backbenchers, because the Conservative party is now so divided, I don’t know. Let’s wait and see," he says.

Chris Mason
Political editor

Image source, PA Media

Re-establishing devolved government in Northern Ireland is the ultimate prize, but is not being talked up much right now by government sources.

They hope, of course, that it might follow in time - but that is far from certain. The DUP, having sounded rather sceptical, have now gone rather quiet.

Remember, there are a range of voices within the DUP.

What Downing Street will hope for is that the party formally says it will go away and look at the deal, and examine it in detail, rather than instantly and loudly reject it.

Then there are Tory Brexiteers. Some are now in government, and some are won round.

But Mark Francois, the chairman of the European Research Group of Tory backbenchers, is not convinced.

And then, there is one Boris Johnson. What might he say or do, and how much grief might he fancy causing the prime minister? We'll soon find out.

The prime minister may not have done enough in his negotiations with the EU to win over the DUP, says Brexiteer and former cabinet minister Jacob Rees-Mogg.

The DUP - the largest unionist party in Northern Ireland - objects to current trade arrangements for Belfast. It's refused to take part in the Northern Ireland Assembly, causing this to be suspended.

Appearing on ITV's Good Morning Britain programme, Rees-Mogg says: "From what I've heard, he (Rishi Sunak) has done very well, but I'm not sure he has achieved the objective of getting the DUP back into power-sharing, which is the fundamental point of it."

Rees-Mogg says the view of the DUP will be "influential among Conservative MPs". He adds: "I'm afraid with all the EU deals, the devil is in the detail."

Image source, Getty Images

Northern Ireland’s power-sharing system of government was introduced in the 1990s, to try to end decades of violence.

The Northern Ireland Assembly has power over the economy, education and health, though other policy areas are still controlled by London.

Any Assembly government has to have input from both nationalists (who want unity with the Republic of Ireland), and unionists (who want to remain part of the UK).

The Assembly has not fully functioned for the past 12 months as the result of a protest by the Democratic Unionist Party (DUP) against the Northern Ireland Protocol.

The Protocol is an arrangement which was set up after the UK left the European Union to preserve the smooth flow of goods across the border between Northern Ireland and the Republic of Ireland - which remains in the EU.

The DUP, Northern Ireland's largest unionist party, believes this arrangement weakens Northern Ireland’s bond with the rest of the UK.

In February 2022, it pulled its first minister out of Stormont's devolved government, and has refused to return to power-sharing until its concerns over the protocol are resolved.

Image source, Reuters

It's "crucial" that Parliament is allowed to vote on any deal agreed between the UK and EU, says Theresa Villiers, a former Northern Ireland secretary who backed Brexit.

Villiers tells BBC Radio 4's Today programme she will make a decision on whether or not to support the deal "dependent on what it contains".

In coming to her view, she confirms that she'll be speaking to members of the DUP. The party opposes the current trade arrangement for Northern Ireland - an issue which has caused a political shutdown in the Northern Ireland Assembly.

Villiers says any deal must address the ongoing "friction" in trade between Northern Ireland and the rest of the UK, and the fact Belfast's current position leaves it "subject to thousands of single market laws over which they have no say".

Although the government has the power to go ahead and strike a deal with the EU, Villiers says there's a "vital need for Parliament to have its say and to have a vote on this".

Nick Eardley
Chief political correspondent reporting from Windsor

Good morning from Surrey where the prime minister and European Commission President will be meeting soon to sign off on new Brexit arrangements.

We're told there are still final talks to take place. Officials have continued discussing the specifics of the deal over the weekend. But it's extremely likely we'll be poring over them by this evening.

If Rishi Sunak signs on the dotted line, the prime minister will begin his big sell immediately at a press conference. I'd expect him to argue his deal will remove trade barriers with between Great Britain and Northern Ireland.

No 10 will also want to pitch this as a deal that protects the union and gives politicians in NI more of a say over the rules that govern them (we're told that's one of the final things being thrashed out today).

The hardest sell will be in Parliament, where the PM will deliver a statement later. The DUP and Tory Brexiteers will then pore over the details of legal texts, which could take a few days.

But many Tory MPs are sceptical and some think the prime minister will struggle to get the DUP on board.

Image source, Getty Images

We're still waiting to see if any deal is unveiled by the EU and UK - but our Brussels correspondent Jessica Parker has taken a look at what an agreement could cover.

• Green and red lanes: Products that are staying in Northern Ireland will go through a green lane, undergoing fewer checks and less paperwork - a key question is how much these are reduced. Goods headed for the Republic of Ireland and rest of the EU would go through a red lane
• The European Court of Justice: A key issue is who settles disputes over the Northern Ireland Protocol. The European Commission wants it to be the European Court of Justice. The UK's original position was that the ECJ's oversight role be entirely removed, but we may see language that will downplay the court's importance and emphasise other arbitration routes
• State aid and VAT: Businesses in Northern Ireland follow EU rules on state aid and VAT, meaning tax breaks and UK government payments to help firms in NI must be within limits set by the EU. The UK government wants to remove these limits. There could be "fudge" in those areas which have, ultimately, proved less totemic than the Irish Sea trade border and governance

Read more here

Chris Mason
Political editor

"Let's hope this is one of the last great rollercoaster moments of Brexit."

So said one government figure to me, anticipating an important moment today - but worldly enough to realise it's not necessarily the end of the story.

These negotiations, between the government and Brussels, the government and Conservative backbenchers, and the government and Northern Ireland's Democratic Unionist Party(DUP), have resembled diplomatic Jenga - wobbly bricks here, there and everywhere.

One element has been all but done for a while, and, we expect, to be sorted today - the deal between London and Brussels.

I’m told Prime Minister Rishi Sunak and European Commission President Ursula von der Leyen will talk about dealing with what some in London regard as a "democratic deficit" for Northern Ireland - that it needs more of a say about future changes in EU rules that will have an impact there.

But let's be clear: the European Commission head would not be coming here unless it was sorted.