King Charles has been pictured for the first time since his cancer diagnosis was announced on Monday evening
Both he and Queen Camilla travelled to the royal estate in Sandringham by helicopter
Earlier, Prince Harry arrived in London to visit his father - he flew in from his home in California
We understand there are no plans for him and his brother William to meet during his trip to the UK
Buckingham Palace announced the King's cancer was found during his recent treatment for a benign enlarged prostate
The monarch has postponed public duties, but will continue state duties and will still meet the prime minister weekly
We've been waiting for Prince Harry's arrival at Heathrow for a little while now.
There's been no sighting of the Duke of Sussex yet, but we have seen a number of black 4x4 cars coming and going.
As we've been reporting, the King called his younger son personally to give him the news of his cancer diagnosis, which led Prince Harry to take the long journey from California to see his father in person.
Damian Grammaticas
Political correspondent
The prime minister began his weekly cabinet meeting this morning by wishing the King well, Rishi Sunak's official spokesman has told reporters.
Speaking at the regular briefing in Downing Street, the spokesman said Sunak told his assembled ministers "all of our thoughts would be with His Majesty and we wish him a speedy recovery".
Sunak said this morning the King's cancer had been "caught early" - but the spokesman didn't elaborate on whether the PM had been briefed on his condition.
Image source, EPA
Image source, EPAWe've been reporting on the good wishes sent to the King by many people around the world.
And students at the Gurukul School of Art in Mumbai have spent the day painting portraits of him.
Working in the middle of the street, the students painted 'get better soon' messages on giant canvases.
As we've reported, Prince Harry is expected to arrive in London soon to see his father.
This picture from Heathrow Airport - taken outside Terminal 5 a short time ago - shows the photographers ready to get their shot.
King Charles Diagnosed With Cancer: Your Questions Answered
You can watch a special programme answering your questions on the King's cancer diagnosis now.
Watch King Charles Diagnosed With Cancer: Your Questions Answered by pressing the programme's play button above.
We'll also bring you text updates here.
Sean Coughlan
Royal correspondent
Image source, ReutersPrince Harry, pictured last year
It’s been a rapid response from Prince Harry to hurry from California to visit his father in the UK - he's expected to arrive in London shortly.
Such emergencies can bring people together and it follows a personal conversation where the King broke the news to his son.
There had already been signs of a family getting closer, with Prince Harry calling the King for his 75th birthday in the autumn. But until now there had been few signs of Prince Harry heading over for family events, staying in the US with Meghan and their children over Christmas.
It remains to be seen whether this will be a flying visit - or whether there will be a longer-term sea change.
Prince Harry and Meghan had already seemed to be getting warmed up for some more travel this year. They were recently spotted at a movie premiere in Jamaica and had flagged a trip later this month to an event in Canada related to the Invictus Games.
Will the UK now be a more regular stop on their itinerary?
So what does this diagnosis mean for the King, for the Royal Family, and for the UK?
We will be be answering your questions at 12:30 GMT with a live panel of experts, including a cancer specialist and royal historian.
You'll be able to watch live at the top of the page, and follow along with text updates here.
In some cases a selection of your comments and questions will appear on screen, displaying your name and location as you provide it unless you state otherwise. Your contact details will never appear.
Image source, ReutersKing Charles speaks with the prime minister of the Bahamas, Philip Davis, in 2022
We’ve been getting more reaction from Commonwealth realms – countries where King Charles remains the head of state.
Already we’ve heard from Canada and Australia, with the respective prime ministers letting the King know he was in their thoughts.
Now the prime minister of the Bahamas, Philip Davis, commends the King for his “openness" in sharing his cancer diagnosis, adding that he's shining a light on “a challenge faced by many around the world”.
"Stay strong" is the message from New Zealand's prime minister, Christopher Luxon - using the Māori phrase "kia kaha" on behalf "of all Kiwis".
Sean Coughlan
Royal correspondent
Image source, ReutersThe King, pictured last month
After bombshell royal announcements such as yesterday’s news about the King’s cancer diagnosis, there’s a huge public demand for more information.
But don’t expect to hear much more of the specifics of the health problem or the treatment, with Buckingham Palace not planning to provide regular updates on the King’s condition.
So it’s worth managing expectations on what further details might be added, at least in the short term.
It follows a familiar pattern with royal news, where an initial statement is issued, which prompts intense media discussion and many responses.
But after that there can be few extra clear facts, despite a howling blizzard of speculation.
When it’s a question of someone’s health, there’s even more reason to expect privacy and the information provided is already deeply personal for any family.
So the focus will switch to the reactions and well-wishers and other sources of information. And today Prime Minister Rishi Sunak has gone further than the Palace statement, in saying the cancer’s been caught early.
Charlotte Gallagher
Reporting from Buckingham Palace
Image source, EPAThe Royal Standard at Buckingham Palace on Tuesday
The Royal Standard is flying at Buckingham Palace, meaning the King is staying at his London home, Clarence House, just a few minutes walk up the Mall.
Thousands of tourists are here to see the Palace, but they’re also taking photos of the hundreds of journalists that are reporting on the story.
News crews from countries such as the US, Australia, Japan and Brazil are here, such is the huge global interest in the Royal Family.
Image source, Daily Mirror/PAKing Charles III and Queen Camilla at the launch of The Coronation Food Project, which aims to bridge the gap between food waste and food need, November 2023
King Charles is stepping back from public duties, with other royals stepping up to cover some of the engagements.
But covering them all will prove difficult - with 425 listed engagements in 2023, Charles was second only to Princess Anne in how many he undertook last year.
For a flavour of the King's workload, here just some of those 425 engagements, as listed by the Court Circular , external- the official record of royal engagements:
Image source, ReutersThe world's media have joined the usual crowds of tourists at Buckingham Palace this morning
Tourists outside Buckingham Palace say their thoughts are with the King after his cancer diagnosis.
Canadian visitor Justin Haden, 52, says he was "sad" hearing of Charles's illness and hopes he will "make a recovery".
Lisa Nash, 61, says she loves the Royal Family, adding they do "a lot for this country".
She sympathises with Charles's "struggle" but is "sure he'll pull through and things will be fine".
Martin Harris, 43, from Northampton, says the news is a “shame for the family more than anything”.
"You think of the family like you would do your own family," he adds.
Image source, ReutersAs we've reported, well-wishes for the King have come in from around the world since yesterday evening. The prime minister of Barbados is the latest - she wishes King Charles a “full and speedy recovery”.
“It is with great sadness that I learned of the illness of His Majesty the King,” Mia Mottley, Barbados' first female PM, wrote on X.
She also offers her “best wishes to Queen Camilla and the rest of the royal family”.
Barbados removed the late Queen Elizabeth as head of state in November 2021, becoming a republic.
So what does this diagnosis mean for the King, for the Royal Family, and for the UK?
We will be be answering your questions at 12:30 GMT with a live panel of experts, including a cancer specialist and royal historian.
You'll be able to watch live at the top of the page, and follow along with text updates here.
In some cases a selection of your comments and questions will appear on screen, displaying your name and location as you provide it unless you state otherwise. Your contact details will never appear.
Image source, GordonstounA young King Charles arrives at Gordonstoun, accompanied by the Duke of Edinburgh, to his left
Since the news broke last night, King Charles has received messages of support from around the world.
Among the well-wishers is Lisa Kerr, the principal of Gordonstoun School, north-east Scotland, where Charles spent his formative years.
She tells the BBC's Good Morning Scotland programme: "We were all very shocked to hear the news last night, particularly having seen the King doing so well out and about after his prostate treatment."
But Kerr says she is "hugely encouraged by his wholly positive attitude to his diagnosis and his continuing commitment to service".
Image source, PA MediaKing Charles with headteacher Jane Gardener in January this year, during a visit to a school in Norfolk
As we've reported, the King will continue his state duties and paperwork while he's treated for cancer - but has postponed his public duties.
Dame Julia Cleverdon - who spent 16 years as chief executive of Business in the Community, external, a charity linked to the King - says he will be "very disappointed" as he "loves work".
She tells BBC Radio 4's Today programme the King has "absolutely flourished" in the past two years and will be "totally determined to recover fast and well".
We haven't had an update from Buckingham Palace today - so here are the main lines from yesterday's announcement, which came at 18:00 GMT.
Image source, PA MediaThe Prince of Wales is expected to return to royal duties on Wednesday - his first public service since his wife had abdominal surgery last month.
He is due to host an investiture ceremony at Windsor Castle tomorrow, before attending the London Air Ambulance annual fundraising gala in London.
Prince William’s return to work arrives at a difficult moment for the 41-year-old heir to the throne.
He will not only carry out engagements without Kate - who isn’t expected to return to public duties until after Easter - by his side. But he will also be tasked with covering some of the King’s public duties in the coming weeks.
His brother, Prince Harry, is returning to the UK, after reportedly being seen at Los Angeles airport last night. But the brothers' relationship is strained - and it's not known if they will meet.
Image source, PA MediaKing Charles meeting the Archbishop of Canterbury in April last year
Justin Welby, the Archbishop of Canterbury, says he is "praying for the King and his family - for God’s comfort and strength in the weeks and months to come".
In the social media post, external, Welby - who is currently in Ukraine meeting faith leaders - wishes His Majesty a "swift and full recovery".
The Archbishop of Canterbury crowned King Charles in the Coronation ceremony last year.
Image source, Getty ImagesKing Charles has done a great thing by sharing his cancer diagnosis with the public, says Lord Dobbs.
The Conservative peer - perhaps best known as author of the House of Cards novels - knows the King and Queen, and was born on the same day as Charles.
Taking an optimistic view, Dobbs - who is a cancer survivor himself - tells the Today programme it is "easy to overdo the gloom".
The disease is "eminently survivable", and the Palace's announcement encourages the public not to treat it as something "appalling".
Getting an early diagnosis, Dobbs says, is "safer, it's simpler, and it gives much greater survivability".
"It's a modern look from a modern monarchy about a very old-fashioned problem."