On Monday the prime minister will welcome not only the Ukrainian president, but also E3 allies France and Germany to discuss the state of the war in Ukraine.
French President Emmanuel Macron and German Chancellor Friedrich Merz will join Sir Keir in showing solidarity and support for Ukraine and its leader, but it's the update on the peace negotiations that will be the main focus of the meet up.
The four leaders are said to be set to not only discuss those talks between Ukraine, the US and Russia, but also to talk about next steps if a deal were to be reached and what that might look like.
Ahead of the discussions, Sir Keir spoke with the Dutch leader Dick Schoof where both leaders agreed Ukraine's defence still needs international support, and that Ukraine's security is vital to European security.
But while Russia's war machine shows no signs of abating, a warm welcome and kind words won't be enough to satisfy the embattled Ukrainian president at a time when Russian drone and missile attacks continue to bombard Kyiv.
What is the latest in negotiations?
Over the weekend, Mr Zelenskyy said he had discussed "next steps" with US President Donald Trump's advisers and was "determined to keep working in good faith".
"The American representatives know the basic Ukrainian positions," Mr Zelenskyy said in his nightly video address. "The conversation was constructive, although not easy."
But on Sunday evening, ahead of an event at the Kennedy Center, President Trump said he was "disappointed" with Mr Zelenskyy, as was asked about the next steps in Russia-Ukraine talks following negotiations.
He said: "We've been speaking to President Putin and we've been speaking to Ukrainian leaders, including Zelenskyy, President Zelenskyy.
"And I have to say that I'm a little bit disappointed that President Zelenskyy hasn't yet read the proposal. That was as of a few hours ago.
"His people love it. But he hasn't - Russia's fine with it. Russia's you know, Russia, I guess, would rather have the whole country when you think of it. But Russia is, I believe, fine with it, but I'm not sure that Zelenskyy's fine with it. His people love it but he hasn't read it."
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On Saturday, Keith Kellogg, Trump's outgoing Ukraine envoy, had told the Reagan National Defence Forum that efforts to resolve the conflict were in "the last 10 metres".
Kremlin spokesman Dmitry Peskov praised new US security strategy over the weekend, adding that Russia hopes this would lead to "further constructive cooperation with Washington on the Ukrainian settlement".
One Thai soldier was killed, and eight others wounded, according to Thai army spokesperson Major General Winthai Suvaree, who also said Cambodian troops fired first into Thai territory.
Thailand used aircraft "to strike military targets in several areas to suppress Cambodian supporting fire attacks," he added.
In Cambodia, Met Measpheakdey, deputy governor of Oddar Meanchey province, wrote in a Facebook post that three civilians had been seriously injured.
Cambodian officials said the Thai military attacked their troops first in Preah Vihear province.
"Cambodia urges that Thailand immediately stop all hostile activities that threaten peace and stability in the region," said Cambodian defence ministry spokesperson Maly Socheata.
Tensions have simmered since the neighbouring countries signed a US-brokered ceasefire agreement in October, put forward by President Donald Trump.
Their territorial disputes led to five days of combat in July that killed dozens of soldiers and civilians.
Thai Prime Minister Anutin Charnvirakul said that military operations would be carried out as necessary to defend the country and protect public safety.
"Thailand has never wished for violence. I'd like to reiterate that Thailand has never initiated a fight or an invasion, but will never tolerate a violation of its sovereignty," he said.
In Thailand, more than 385,000 civilians across several border districts are being evacuated, with over 35,000 already housed in temporary shelters, military officials said.
Meanwhile, the Cambodian Education Ministry said several schools along the border had been shut.
Footage posted online showed what appeared to be students hurriedly leaving classes to meet their parents.
Malaysia's Prime Minister Anwar Ibrahim urged Thailand and Cambodia to "exercise maximum restraint".
In a post on social media, he added: "Our region cannot afford to see long-standing disputes slip into cycles of confrontation."
Si Sa Ket, Surin and Ubon Ratchathani provinces in Thailand, and Cambodia's Preah Vihear and Oddar Meanchey provinces were among the areas said to be caught up in the latest clashes.
On Sunday, both nations accused each other of opening fire along the border in what the Thai army said was an incident that lasted around 20 minutes and resulted in the injury of two of its soldiers.
But Cambodia said that the Thai side fired first and that Cambodian troops did not retaliate.
Read more:
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For more than a century, Thailand and Cambodia have contested sovereignty at points along their 508-mile (817km) land border.
The Atlantic Bastion programme, announced as part of the Strategic Defence Review, will combine autonomous vehicles and AI with warships and aircraft to identify threats to underwater structure and to defend them.
The Ministry of Defence (MoD) said it was "in direct response to a resurgence in Russian submarine and underwater activity", including the spy ship Yantar, which was tracked around UK waters last month.
The project has attracted a combined investment of £14m from the MoD and industry this year, with hopes the technology can be deployed next year.
A total of 26 firms from the UK and Europe have submitted proposals for the project.
Last week Defence Secretary John Healey visited Portsmouth Naval Base to examine some of the early technology which could be used as part of Atlantic Bastion.
It included the SG-1 Fathom, an underwater glider; Rattler, an unmanned remote-controlled boat; a model of an autonomous anti-submarine helicopter called Proteus; and an uncrewed experimental submarine called Excalibur.
"People should be in no doubt of the new threats facing the UK and our allies under the sea, where adversaries are targeting infrastructure that is so critical to our way of life," Mr Healey said.
"This new era of threat demands a new era for defence, and we must rapidly innovate at a wartime pace to maintain the battlefield edge."
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The launch of Atlantic Bastion coincides with a speech from the First Sea Lord General Sir Gwyn Jenkins at the International Sea Power Conference in London on Monday.
Sir Gwyn is expected to say: "The SDR [Strategic Defence Review] identified the maritime domain as increasingly vulnerable - and that maritime security is a strategic imperative for the UK. It is time to act.
"This begins with Atlantic Bastion - our bold new approach to secure the underwater battlespace against a modernising Russia."
The MoD spokesman said: "Atlantic Bastion will see ships, submarines, aircraft and unmanned vessels connected through AI-powered acoustic detection technology and integrated into a digital targeting web - a pioneering network of weapons systems that allow battlefield decisions for targeting enemy threats to be made and executed faster."
Subsea infrastructure is the lifeblood of the UK's connectivity, carrying 99% of international telecommunications data and vital energy supplies such as electricity, oil and gas.
Read more from Sky News:
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UK undersea cables are vulnerable
On Thursday, the UK and Norway signed a defence agreement allowing their navies to operate a combined fleet of warships.
The pact is aimed at protecting critical undersea cables.
The US president acknowledged in remarks to reporters there "could be a problem", acknowledging concerns over the streaming giant's market dominance.
Crucially, he did not say where he stood on the issue.
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It was revealed on Friday that Netflix, already the world's biggest streaming service by market share, had agreed to buy Warner Bros Discovery's TV, film studios and HBO Max streaming division.
The deal aims to complete late next year after the Discovery element of the business, mainly legacy TV channels showing cartoons, news and sport, has been spun off.
But the deal has attracted cross-party criticism on competition grounds, and there is also opposition in Hollywood.
The Writers Guild of America said: "The world's largest streaming company swallowing one of its biggest competitors is what antitrust laws were designed to prevent.
"The outcome would eliminate jobs, push down wages, worsen conditions for all entertainment workers, raise prices for consumers, and reduce the volume and diversity of content for all viewers."
Republican Senator, Roger Marshall, said in a statement: "Netflix's attempt to buy Warner Bros would be the largest media takeover in history - and it raises serious red flags for consumers, creators, movie theaters, and local businesses alike.
"One company should not have full vertical control of the content and the distribution pipeline that delivers it. And combining two of the largest streaming platforms is a textbook horizontal Antitrust problem.
"Prices, choice, and creative freedom are at stake. Regulators need to take a hard look at this deal, and realize how harmful it would be for consumers and Western society."
Paramount Skydance and Comcast, the parent company of Sky News, were two other bidders in the auction process that preceded the announcement.
The Reuters news agency, citing information from sources, said their bids were rejected in favour of Netflix for different reasons.
Paramount's was seen as having funding concerns, they said, while Comcast's was deemed not to offer so many earlier benefits.
Paramount is run by David Ellison, the son of the Oracle tech billionaire Larry Ellison, who is a close ally of Mr Trump.
The president said of the Netflix deal's path to regulatory clearance: "I'll be involved in that decision".
On the likely opposition to the deal. he added: "That's going to be for some economists to tell. But it is a big market share. There's no question it could be a problem."
A yellow weather warning for rain comes into effect from 6pm on Monday, and will be in place for 24 hours, covering parts of southwest England and Wales, and stretching to parts of Herefordshire and Hampshire.
The Met Office has also issued a yellow warning for high winds from Dorset to Cornwall and up to north Wales, in place from 10pm on Monday until 4pm on Tuesday.
It said transport networks could face disruption, with delays for high-sided vehicles on exposed routes and bridges, and coastal roads and seafronts affected by spray and large waves. Power outages are also possible.
For 24 hours from 6pm on Monday, up to 40mm of rain could fall in some areas, with 60-80mm of rain over Dartmoor and high ground in South Wales, which would amount to more than half the average monthly rainfall in December.
Check the weather forecast where you are
The predicted rainfall across southwest England and South Wales is expected to hit already saturated ground and could lead to difficult travel conditions.
Another rain warning is in place for northwest England from midnight on Tuesday until 3pm, while a wind warning has been issued for northwest Scotland from 3pm on Tuesday until 10am on Wednesday.
The Met Office's deputy chief meteorologist, Steven Keates, said: "A deepening area of low pressure will approach the UK from the southwest later on Monday, bringing with it heavy rain and strong winds, which are likely to affect the UK between late Monday and early Wednesday.
"The exact track, depth and timings of this low are uncertain, which makes it harder to determine where will be most impacted by strong winds and/or heavy rain.
"This system has the potential to cause disruption, and severe weather warnings are likely to be issued over the weekend as details become clearer. We therefore urge people to keep up-to-date with the latest Met Office forecast."
The Met Office said the rest of the month remained unsettled, with further periods of low pressure predicted.
It also said it is too early to provide an accurate forecast for the Christmas period.