Jack Fenwick
Political correspondent

Many of those opposed to this deal have voiced concerns about what this could mean for the UK's security.

They say that the close ties between Mauritius and China would put the UK's interests at risk.

Today, the prime minister took that argument head on.

He said that without this deal, the UK would be unable to "prevent China or any other nation setting up their own bases on the outer islands".

That was a scenario that he said "no responsible government" would allow to happen.

The prime minister said that the nations who wanted this deal to collapse included China, Russia and Iran - and he accused Conservative leader Kemi Badenoch and Reform UK leader Nigel Farage of being "in this column" when it comes to the issue of Chagos.

Image source, UK government

The deal handing over the Chagos Islands from the UK to Mauritius has been published, external - it includes details of more UK funding for Mauritius, on top of the £101m annual cost to lease the Diego Garcia base. Here are some extracts:

• Mauritius is sovereign over the Chagos Archipelago in its entirety, including Diego Garcia
• The United Kingdom shall have full responsibility for the defence and security of Diego Garcia
• Mauritius is free to implement a programme of resettlement on the islands of the Chagos Archipelago other than Diego Garcia
• The United Kingdom agrees: to pay Mauritius an annual sum; to capitalise a Trust Fund for the benefit of Chagossians as established by Mauritius; to grant multi-year funding as part of a development framework for projects to be undertaken by Mauritius across 25 years
• The arrangements for such payments, including amounts and modalities, shall be agreed separately
• This agreement shall have a duration of 99 years...this agreement may be extended for a further 40 years

James Landale
Diplomatic correspondent

Critics of the Chagos deal are clear: the government should not give up British territory at what they see as huge cost to the taxpayer and a weakening of our security. So why has the UK government taken this decision?

Put simply, it believed the military base at Diego Garcia would otherwise become unworkable. Ministers feared an “advisory opinion” by the UN’s International Court of Justice - that the Chagos Islands belonged to Mauritius - would soon become a legally binding judgement by a special tribunal that governs international laws of the sea.

In such a case, they argue Diego Garcia’s satellite communications would be threatened because the UK relies on a UN authority to get access to a particular electromagnetic spectrum.

They say contractors would refuse to visit the isolated base - to make repairs or deliver supplies - for fear of being sued. The ability to fly in and out might be challenged by international rules that govern our skies.

Without the deal, officials say, there would be no legal ban preventing Mauritius allowing a foreign power such as China to establish a military or other presence in the islands.

Without the UK’s annual payment, they argue, Mauritius would have a financial incentive to open the islands up to Chinese investment.

More broadly, with a deal, the UK government can continue to criticise Chinese aggression in the South China Sea without facing accusations of hypocrisy.

The UK can also avoid losing further diplomatic support across the world which overwhelmingly thought the islands belonged to Mauritius.

Image source, PA Media

There's been a lot of information to digest over the last 50 minutes or so. Here are some of the key details on the Chagos deal that the government has just announced:

• Prime Minister Sir Keir Starmer says the island of Diego Garcia will continue to be used as a military base in a deal signed off by key allies, including the United States, Canada, Australia and New Zealand
• The British government says it will lease the use of the territory from Mauritius for a period of 99 years at a cost of £101m per year
• The net value of the payments under the treaty will reach £3.4bn, according to a government press release
• Under the terms of the deal, the UK will hand sovereignty of the islands to Mauritius
• Starmer says the government had to "act now" as it would not have a "realistic prospect of success" if Mauritius restarted legal proceedings
• Starmer has also hit out at the Conservatives and Reform UK - who have both stated their opposition to the deal
• Defence Secretary John Healey says "no action was no option," and anyone arguing to abandon the deal would abandon the military base
• British citizens and the British armed forces are safer today and in the future because of the deal, he adds

More now from the press release issued a little while ago.

In it, Defence Secretary John Healey says "international legal proceedings could have rendered the base inoperable" which would have affected the UK's national security.

Without a deal, provisional measures in a tribunal under the Law of the Sea Convention would have impacted "the ability of the Armed Forces to patrol the waters around the base," he says.

The government says there will be "robust provisions" to keep adversaries out of the military base on Diego Garcia.

This includes a "24 nautical mile buffer zone" where nothing can be built without UK consent.

Foreign security forces will also be banned on the outer islands, where there will be joint decision making to prevent wider activities from disrupting base operations.

The government says there is a "binding obligation" in place to ensure the base is never undermined.

Let's bring you more details of the deal signed today.

In a government press release, Defence Secretary John Healey says "the UK retains full operational control of Diego Garcia" under the terms of the deal.

That includes "management of the electromagnetic spectrum satellite used for communications", which Healey says is "vital for countering hostile interference."

A reminder, sovereignty of the Chagos Islands, formally the British Indian Ocean Territory, will be handed to Mauritius.

Image source, EPA

A journalist from the Financial Times asks for more clarity on cost.

Shouldn't the figure actually be closer to £10bn rather than £3.4bn if you multiply the average yearly cost of £101m across the deal's 99 years?

Starmer responds that £3.4bn is the "net cost", and explains that this is how the government and the Office for Budget Responsibility measures spending on similar projects.

The prime minister is also asked whether he will be asking allies - including the US - to contribute to payments.

He says that the US will be paying the "running costs" of the base.

"There are different contributions to different aspects," he says.

We're leaving Keir Starmer's press conference there, and we'll shortly get you up to speed with all the key details.

Next up, Starmer is asked how the government is paying millions of pounds for this deal while also making cuts to the welfare budget, including disability benefits.

Starmer says that the "first duty of a prime minister is to keep the country safe" and the Diego Garcia island is vital for this with its capabilities having "already had huge impact around the globe in relation to combating and defeating our adversaries."

The next question from our defence correspondent Jonathan Beale is to Healey.

He asks him whether the funds are coming out of the UK's defence budget.

Healey says the deal is an "essential investment in our national security" and accounts for less than 0.2% of the UK's defence budget.

Britain's armed forces are "safer and stronger because of what we do in Diego Garcia", he adds.

Starmer jumps in and takes aim at the Conservatives and Reform UK - who have both stated their opposition to the deal.

"Surprisingly, the leader of the opposition and Nigel Farage are in that column [against the deal], alongside Russia, China and Iran," he says.

As a reminder, Conservative leader Kemi Badenoch says the UK should not be paying to "surrender British territory to Mauritius", while deputy leader of Reform, Richard Tice, called the deal a "Starmer surrender sell out".

Image source, EPA

The BBC's Jonathan Beale has the first question for Starmer, asking the prime minister how he responds to Chagossians who don't want to hand control of the territory to Mauritius.

Starmer says the Chagossian challenge was a "good thing" as it allowed the court to come down in favour of the UK after hearing legal arguments for and against the deal.

Beale also asks the PM to spell out the exact cost of the deal.

Starmer says the costs set out - £101m a year - is an "average cost" and therefore the net overall cost is £3.4bn over 99 years.

He says this average yearly cost is about the same, or slightly less, than running an aircraft carrier, minus the aircraft.

Measured against these costs, he argues, this deal is "very good value for money".

We're now hearing from senior British Army officer Gen James Hockenhull.

He says that the base's location provides "immense global reach", making it a "unique asset" for British security.

"I welcome the long-term certainty that this treaty brings. It will help the British Armed Forces in our efforts to support stability abroad and security at home," Hockenhull says.

Defence Secretary John Healey says that the UK faced the prospect of new legal rulings within a few weeks that would have weakened its sovereignty over the base, claiming that in years the base would have become "inoperable".

"That's why we've taken action," he adds, saying that Britain's allied nations were behind it with this deal.

He adds that China, Russia and Iran wanted to see the deal collapse.

"No action was no option," he says, adding that anyone arguing to abandon this deal would abandon the base.

British people and British armed forces are safer today and in the future because of this deal, Healey says.

Wrapping up his speech, Starmer says the deal signed today is "the only way" to maintain the Diego Garcia base in the long term.

"There is no alternative," he adds, stressing that the decision has been taken to protect national security.

"By agreeing to this deal now on our terms, we're securing strong protections, including from malign influence, that will allow the base to operate well into the next century, helping to keep us safe for generations to come," he says.

With that, Starmer hands over to Defence Secretary John Healey.

Starmer says if the UK did not agree to a deal, it would not have been able to prevent other nations from setting up a base on the island.

He says that the deal means the UK is agreeing to "strong protections".

He then criticises the former Conservative government, and leaders including former Prime Minister Boris Johnson, who he says failed to conclude an agreement.

Image source, EPA

It is not just about international law, Starmer says, but also about the operation of the base.

The prime minister says one example is the electromagnetic spectrum, as its use is "key" to understand and anticipate those wishing to interfere and destruct the capability and harm the UK's interests.

If the UK's right to control it was put into doubt, then the country would lose the first line of defence.

He says "no responsible government" could let the UK lose such capabilities.

Speaking to journalists, the prime minister stresses that the UK cannot cede ground to others that might seek to harm the UK.

"We had to act now," he says, warning that the base was under threat as a result of court decisions.

Starmer says that if Mauritius restarted legal proceedings, the UK would "not have a realistic prospect of success".

He adds that President Trump backs the deal.

"Almost everything we do from the base is in partnership with the US.

"President Trump has welcomed the deal along with other allies, because they see the strategic importance of this base and that we cannot cede the ground to others who would seek to do us harm."

We can now bring you more detail on the deal signed between the UK and Mauritius, which has now been confirmed by the British government.

In a press release, the government says the cost of leasing the use of the territory from Mauritius is £101m per year.

The net value of the payments under the treaty will reach £3.4bn, the government adds.

The government says the island of Diego Garcia will continue to be used as a military base, and this agreement has been signed off by the five eyes alliance of intelligence partners - that's the UK, United States, the United Kingdom, Canada, Australia, and New Zealand.

On the importance of the Diego Garcia military base, Starmer says it gives the UK and the US access to "vital capabilities".

"The strategic location of this base is of the utmost importance", Starmer says, adding "the base is right at the base of our security".

Image source, EPA

Prime Minister Sir Keir Starmer is speaking to reporters about the Chagos Islands deal.

You can follow the press conference by hitting watch live at the top of this page.