Well, now President Zelensky, after those talks, says he is still willing to sign a minerals deal with America, but security guarantees are still necessary.

Zakir Starmer, hosting the summit, said any peace deal must respect Ukraine's sovereignty and at the heart of any agreement must be the United States.

After the meeting, President Zelensky flew to Sandringham to meet the King, with the two men spending just under an hour together.

Well, what do Russians think of all this?

We'll be live in Moscow, but first, Chris Mason has our top story.

Early spring sunshine in central London, a few hundred yards from Buckingham Palace, this mansion on the Mall, Lancaster House.

This is what the leaders here wanted today to be about, securing our future.

The hour is Europe and Canada and the host, Zakir Starmer, who told the BBC this morning that he wants to bring together those countries like the UK, keen to act quickly and do the most.

We need to be clear what a European security guarantee would look like.

I do acknowledge that that's more likely to be, in the first instance, a coalition of willing.

In other words, we've got to find those countries in Europe that are prepared to be a bit more forward-leaning.

And after Friday night's spat in the White House...

Mr President, can you get things back on track today?

The Prime Minister is working with the French President Emmanuel Macron on a plan to stop the fighting and then discuss it with the United States.

Will Donald Trump ever be a reliable partner, sir?

Can Europe come together and come up with a plan?

And the cast list complete with the arrival of President Zelensky of Ukraine.

Would you be willing to apologise to Donald Trump, Mr President?

A leader with plenty to talk about, outside and in.

The Prime Minister and 18 others trying to pull off a balancing act, keeping America on side and putting an arm around Ukraine.

Both matter, Zakir insists, for our safety as well as Kyiv's.

We gather here today because this is a once-in-a-generation moment for the security of Europe.

For around two hours they talked, and then some of them talked to us, the President of the European Commission, saying EU countries will need to increase defence spending massively.

Why?

Listen to the memorable imagery she chose.

It's basically turning Ukraine into a steel porcupine that is indigestible for potential invaders and therefore the focus is not only on the military supply, but also for example securing their energy system and making sure that over time this is a strong and resilient country.

Have you won the argument with European colleagues about stepping up to the plate in terms of money?

Absolutely, we all have understood that after a long time of underinvestment it is now of utmost importance to step up the defence investment for a prolonged period of time.

And what of the North Atlantic Defence Alliance, NATO, America for so long at its heart, but now with an unpredictable president?

I think it was a good meeting, it was a very good meeting, because what you see is European countries stepping up, first of all to make sure that Ukraine has got what it needs to stay in the fight as long as it has to continue.

What we also see is European countries really ramping up to help with security guarantees for the moment when a peace deal would be struck.

Obviously there is no deal yet, there is no ceasefire yet, but we have to prepare for that moment.

The Prime Minister told us those countries up for getting involved in delivering and maintaining peace in Ukraine are now working up their plans.

Those willing will intensify planning now, with real urgency.

The UK is prepared to back this, with boots on the ground and planes in the air, together with others.

Europe must do the heavy listing.

But to support peace in our continent, and to succeed, this effort must have strong US backing.

And he added...

Today I'm announcing a new deal, which allows Ukraine to use £1.6 billion of UK export finance to buy more than 5,000 air defence missiles, which will be made in Belfast, creating jobs in our brilliant defence sector.

After what happened the other night between Presidents Trump and Zelensky, do you feel a greater personal responsibility, alongside President Macron and others, for delivering a workable peace?

And on the Coalition of the Willing, as you've described it today, are you persuading more people to join it?

Thank you.

On the question of responsibility, I do think the United Kingdom should step up and lead.

We have done that historically as a nation, and we need to do it again.

On the Coalition of the Willing, yes, a number of countries have indicated today that they want to be part of the plan that we are developing.

I'll leave them to make their own statements about exactly how they want to make that contribution.

So a number of countries, he says, but we don't know how many.

Earlier, Westminster's biggest opposition parties gave us their take on these fast-moving events, the Conservatives focusing on defence spending.

This is a fundamental question.

When I was in cabinet, we talked about getting to 3% by 2030, and we couldn't make the numbers work.

We need to find a way to make the numbers work, because the world is changing very quickly.

And with things like defence, you can't make a decision at the last minute.

Liberal Democrats have been arguing for some time about the need to work with our European neighbours more closely, whether it's on our economy or on our security, and I think recent developments have shown that that is absolutely the way to go.

For Ukraine's leader after the summit, another appointment.

Tonight, a moment Donald Trump craves, but Volodymyr Zelensky is seeing him already.

He flew to Sandringham in Norfolk, meeting the king.

Ukraine's future, a continent's future.

Today, a big day among many big days.

Europe in an era of war, and Donald Trump.

Chris Mason, BBC News, at Lancaster House.

Well, following his meeting with King Charles, President Zelensky sat down with journalists before returning to Kyiv, and he was asked whether he'd apologise to Donald Trump for the public row at the White House on Friday.

Laura Kunsberg was at that briefing with the Ukrainian leader.

He's resisted Russia's attacks for three long, bitter years of war.

On Friday, he fought off the American president's barbs too.

But after two days of turmoil, tonight, speaking in his own language, President Zelensky wanted to make sure he was understood.

I travelled in the train for 12 hours, then for 11 hours I flew because the president of the United States invited me.

But after Friday's fevered meeting, how can he make peace with President Trump, if that's what's required, in order to bring the real war to an end?

Surely to get the security guarantee that you crave, you do need to rebuild your relationship with President Trump.

Will you, as the White House is still asking you to do, apologise or express any regret for how you handled the meeting?

All that we want from partners is the constructive dialogue, so that they remember who the aggressor is.

Are you willing, in principle, to talk about conceding territory, in principle to express some regret to President Trump, or to sign the minerals deal?

We are constructive, we agreed upon signing it, we are ready to sign it, and honestly, I believe that the United States would be ready as well.

Perhaps there is a need in time to analyse certain things, but I would just want the Ukrainian position to be heard.

Too early to talk concessions, he told us.

Our freedom, our values are not for sale.

But he welcomed proposals from the UK, France and others to offer European troops to guard a potential peace one day.

Yet the warmth of a British welcome and European promises are not the same as the raw power of American backing.

President Zelensky wants all three to bring the agony of his people to an end.

Laura Koensberg, BBC News, Stansted.

We're going to go to Russia.

Steve Rosenberg is live in Moscow for us now.

Lots happening in Europe on all of this, Steve.

What's been the reaction from where you are?

Well, tonight on social media, Dmitry Medvedev, the former Russian president, someone considered to be close to Vladimir Putin, posted this about the London summit.

He called it an anti-Trump, anti-Russian coven, in other words, like a gathering of witches and said that those people who'd taken part wanted the war to continue.

Now, what's interesting about that, I think, is the phrase anti-Trump.

The Russian government newspaper used the same phrase, anti-Trump, on its website tonight in its reporting.

And I think it's clear that after today, Moscow's message to the White House will be, dear President Trump, the Europeans are against you, they're against Russia and they're against peace.

We know what the Russians are against, that is the idea of having European peacekeepers in Ukraine, because Russian officials have made that point several times over the last few weeks.

And again today, Sergei Lavrov, the foreign minister, in an interview said that the plan for peacekeepers in Ukraine is a continuation of attempts to egg on the Kiev regime to fight a war against Russia.

And Russian state television tonight poured scorn on the idea of European peacekeepers.

It said that you could fill Wembley Stadium with the British army and still have room for some of the French army.

All right, Steve, thank you.

Steve Rosenberg there live in Moscow.

Chris and Jeremy are here with me.

To you, Chris, first, what a pickle the prime minister was in, having to walk that fine line between keeping Donald Trump on side and continuing support for President Zelensky.

Has he fallen off that tightrope?

It's so interesting, isn't it?

Because there's Russia, Moscow picking away at that exact vulnerability, that sense of a divided West.

What was striking today, there was a warmth, there was a feeling of camaraderie, I guess in contrast with what we saw in the White House 48 hours ago, but also the soundtrack of a continent collectively thinking that things have got real, that Europe needs to try and re-prop up this plan for peace.

But also a recognition again, Clive, from the prime minister that Europe will need America.

So he's trying to maintain that balance.

Domestically, and this might sound parochial in the context of an international conversation, lots of support here in the UK across politics for what the prime minister is trying to achieve.

He's had a bumpy start domestically in many senses, Kirstarmer, but he has seized this crisis and he is shaping events alongside others.

And of course, big implications of what he's talking about if a deal can be done, talking about soldiers and British airmen and women being involved in keeping the peace.

There's loads more diplomacy to come.

This balancing act will continue.

I think we'll see the prime minister on the road again, trying to maintain that balancing act in the coming weeks, and clearly still a huge amount unresolved. Jeremy, Sir Keir Starmer talking about a coalition of the willing, rumours tonight as well of calls for a one month ceasefire.

This is being reported by Le Monde in France, it's coming from the French.

How would you assess where we are in terms of trying to map out some kind of way forward in reaching some kind of ceasefire or peace deal?

Well, I think first of all, President Zelensky will feel a lot happier going home after this meeting in London than he would have had he taken the direct route from Washington, D.C.

Because he will have all that support ringing in his ears and the possibility it might turn from good wishes into hard, tangible support for Ukraine.

Because at the same time in America, the same messages are coming out, the same kind of things he was hearing there, that he needs to compromise, he might even need to resign, that sort of thing.

And positive stuff going towards Moscow from them too.

A report in the New York Times that the Defence Secretary Hegseth has ordered US Cyber Command to cease offensive cyber operations against the Russians.

And so another thing the Russians might like, while pressure on Ukraine continues.

Now why is this such a hard thing for Kirstarmann and the others to get to a deal?

Well, it's about a lot more than real estate, whatever Mr Trump might think.

It's not a question of how much Putin gets to keep and how much Zelensky has to give up.

For the Ukrainians, it's about sovereignty, it's about independence, it's about being their own boss and not being back under the control of Moscow.

But for Putin, now Putin has said often that he doesn't believe that there is such an independent entity as a Ukraine or a Ukrainian.

And maybe his attitude is echoing a well-known phrase by, a well-known saying by Mr Brzezinski, who was a former American National Security Advisor.

He said, without Ukraine, Russia ceases to be an empire.

And he was saying this when the USSR was falling.

But with Ukraine suborned and subordinated, Russia automatically becomes an empire.

So in other words, for Putin, it's about his place in the world.

So a one-month ceasefire against that, well, it doesn't sound that attractive.

All right.

Jeremy Bowen, international editor.

Chris Mason, political editor.

Many thanks.