We're pausing our live coverage in a moment - but before we do here's the latest on what we know:

• King Charles has a form of cancer, Buckingham Palace announced earlier this evening
• The Palace hasn't revealed what kind, except to say it isn't prostate cancer
• It was spotted when the King was in hospital receiving treatment for benign prostate enlargement

• In a statement - which you can read in full here - the Palace said the King has begun regular treatment and will postpone public duties, although he's still expected to continue with paperwork and private meetings
• The King told his immediate family of his diagnosis personally - and Prince Harry, his youngest son, will fly back to the UK in the coming days from California
• Following the news, politicians, religious leaders and celebrities began sending the King messages of support. In the US, President Joe Biden, who lost his son to cancer, sent a heartfelt message saying that dealing with a cancer diagnosis takes courage
• The Church of England, which the British monarch heads, has written a special prayer for the King's health

Our latest write-up is here. Or read what we know about his diagnosis, and what this means for the other royals.

More now from the King's former communications secretary JulianPayne, who said the Palace will have prepared for a situation like this.

The Palace is "nothing if not excellent at preparation", he said. "So whilst this is an unwelcome surprise, I don't think that it will require a significant new change to some of these structures that are in place."

Payne, who worked for the King and Camilla for five years until 2021, also told the BBC's Newshour programme he's sure the King will be keen to return to his public engagements once and if it is deemed prudent.

"He will be deeply frustrated that he can't go out and meet people.

"He really, really enjoys that. He comes back absolutely fired up from all of the conversations."

Tuesday's UK front pages are of course dominated by news of the King's health.

The headline on The Sun is stark - "King: I have cancer". The Mirror calls it a "shock" and notes that it was his recent prostate operation which led to the diagnosis.

The Times reports that the Palace says Charles is "wholly positive". The i says that the announcement "abandons royal protocol" regarding comment on the monarch's health and The Express says Prince Harry will see his father in coming days.

The Guardian chose not to put a picture of King Charles next to its front-page article, opting for Taylor Swift at the Grammys instead. The Telegraph goes the other way - devoting its entire front to the story, while the Daily Mail headline reports the King is "so grateful they caught it early".

Joining those sending the King messages of support is Republic, a campaign group calling for the monarchy to be abolished.

Republic - which sells T-shirts emblazoned with the slogan "#NotMyKing" - held protests during the King's Coronation last year.

But via its account on X, the group issued a statement, external: "Cancer is an awful disease and we're very sorry to hear of Charles's diagnosis. We wish him a speedy recovery."

Earlier we heard from US President Joe Biden, who was asked about his reaction to King Charles's diagnosis during a campaign event earlier. You can watch what he said above.

Biden - who lost his son, Beau, to cancer - also later released a heartfelt message on X.

We've just heard from Julian Payne, a former communications secretary to the King, who has been speaking to BBC Newsnight.

Payne says the King will "no doubt be frustrated" that he has to step back from his public-facing duties as he will "want to be out working".

However, the King will use his diagnosis to raise awareness, as he did with his recent prostate treatment, Payne adds.

"By putting that in the public domain, I think the NHS inquiries went up by over 1,000%," he says.

Earlier, Payne told the Newshour programme: "He'll be thinking, 'well, if I talk about the fact that I've got to undergo cancer treatment, perhaps this is going to encourage people at home to have conversations tonight.'"

Sean Coughlan
BBC News royal correspondent

The King will pause his public events, although continue with his paperwork and private meetings.

It is understood his weekly audiences with Prime Minister Rishi Sunak will continue and will be in person, unless doctors advise that he limits such contact.

There is a constitutional mechanism for when the head of state is unable to carry out official duties - in that circumstance "counsellors of state" can be appointed to stand in for the monarch.

At present that includes Queen Camilla, Prince William, the Princess Royal, and Prince Edward.

Prince Harry and the Duke of York are no longer called upon as they are non-working royals.

We've been getting some more reaction from international leaders, following messages from the US, Canada and Australia already.

From France, President Emmanuel Macron wrote on X: “Wishing His Majesty King Charles III a speedy recovery. Our thoughts are with the British people. Amitiés.”

Roberta Metsola, the head of the European Parliament, also tweeted to wish the King "a speedy recovery".

"His example of public service and commitment inspires well beyond the borders of the United Kingdom. I know the people of Europe wish him well."

And Ireland's President Michael D Higgins extended his best wishes. A statement said Higgins was "very sorry and concerned" to hear the news.

"The president has sent his best wishes on behalf of the people of Ireland to King Charles for his medical treatment and for his full recovery, as well as to Queen Camilla and his family."

The news of King Charles's diagnosis has made headlines all around the world. Here's a photo from outside the Palace this evening, as journalists report from the scene:

Image source, Reuters

The Church of England has written a prayer for King Charles and shared it to social media, external:

"Father of mercies, grant to Charles our King comfort and sure confidence in you, and keep him in perpetual peace and safety, through Jesus Christ our Lord."

As British monarch, King Charles is the Supreme Governor of the Church of England.

The BBC's medical editor Fergus Walsh explains that King Charles's news could encourage others to get checked.

He says the King has been praised by the Royal College of Physicians for raising awareness.

Aleem Maqbool
Religion editor, BBC News

King Charles takes a keen interest in the workings of the Church of England of which he is the Supreme Governor.

The Archbishop of York Stephen Cottrell reacted to the news about the King’s health saying: “It's come as a bit of a shock. So, my reaction is one of prayerful concern, prayerful hopefulness that this has been diagnosed early and will be treatable. I'm praying for him."

The King is also well known for his fascination with other belief systems. He has long talked of his appreciation for the way people of different faiths, and none contribute to British society. It is of no surprise that a diverse array of faith leaders have sent their prayers.

"On behalf of the entire Catholic community in England and Wales, I offer His Majesty our warmest wishes and assurance of steadfast prayers for his full and speedy recovery. God bless the King,” said Cardinal Vincent Nichols, head of the Catholic Church in England and Wales.

"I know that the Jewish communities of Great Britain and the Commonwealth will join me in wishing him a Refuah Sheleima - a complete and swift recovery,” tweeted Ephraim Mirvis, the UK’s Chief Rabbi.

Among others to comment is Zara Mohammed, secretary general of the Muslim Council of Britain who said: "I am saddened to hear about King Charles' diagnosis and extend my heartfelt wishes for His Majesty's strength and a swift recovery."

Image source, Getty Images

Dickie Arbiter was Queen Elizabeth's press secretary and also the former media manager for the King when was the Prince of Wales.

He tells the BBC World Service’s Newshour programme the King will be frustrated by the confinement of cancer treatment.

"He is pragmatic about it and he is upbeat and he’s carrying on work as usual, albeit on an administrative capacity rather than being seen out and about," Arbiter says.

"And that’s the part that will frustrate him because that’s his job; to be seen out and about by the great British public, by the people of the Commonwealth, by the people of the realms, by business, by industry, by parliamentarians and he’s not able to do that."

Image source, Reuters

The King's cancer diagnosis comes after more than two weeks of reports over his health. Here's a timeline of what's been happening:

• 17 January: Buckingham Palace announces that King Charles will attend hospital for treatment for an enlarged prostate the following week
• 26 January: The King receives his treatment for an enlarged prostate, after being admitted to the London Clinic in the morning. Queen Camilla says of her husband: "He's doing well"
• 29 January: King Charles leaves hospital after three nights. The Palace says he will have to postpone his public engagements "to allow for a period of private recuperation"
• 31 January: The Queen says her husband is "doing his best" after hospital treatment
• 4 February: The King and Queen attend church in Sandringham, with Charles waving at well-wishers, in his first public outing since treatment
• 5 February: The Palace announces that King Charles has been diagnosed with a form of cancer discovered during his recent treatment and he has started "regular treatments"

Image source, Reuters

As we reported earlier, Prince Harry, the Duke of Sussex will travel to the UK to visit King Charles "in the coming days", the BBC understands.

He will be travelling alone, with his wife Meghan remaining in the US with their two children.

It's no secret that the relationship between Prince Harry and Meghan and the rest of the royal family is strained.

Prince Harry's last appearance at a royal occasion took place in May, during the King's Coronation.

While Prince Harry and King Charles have had their differences, they have continued to have a relationship with the duke calling his father on his 75th birthday last year. The King also contacted Prince Harry to tell him of his diagnosis personally.

• Read more here

Image source, PA Media

We've just heard a little more from US President Joe Biden.

Writing on X, he says: "Navigating a cancer diagnosis, treatment, and survivorship takes hope and absolute courage.

"Jill and I join the people of the United Kingdom in praying that His Majesty experiences a swift and full recovery."

Biden's son, Beau, died of brain cancer aged 46, and his long-time friend, Republican Senator John McCain, also died of cancer in 2018.

Image source, EPA

Australian Prime Minister Anthony Albanese has also offered his thoughts to King Charles.

"The thoughts of all Australians are with King Charles and his family," he said from Canberra.

"We wish him very much a speedy recovery. I’ll be sending a message to the Palace this morning and we hope that King Charles has a speedy recovery and a return to his duties as soon as possible."

Like Canada, which we posted about earlier, Australia is a member of the Commonwealth, and the King is the country's head of state.

Fergus Walsh
Medical editor

The King joins 1,000 people a day in the UK who are diagnosed with cancer.

We know that age is the number one risk factor for most cancers. The King is 75 years old, and just over a third of all new cancers are diagnosed in people aged 75 and over.

Most cancer treatment these days is given to people who are outpatients, which is how we are told the King will receive his treatment, but that covers a huge variety of different treatments.

Chemotherapy can be delivered in many different forms, and all treatments come with potential side effects, but because we don't know what type of cancer the King has, we can't speculate as to what treatment he may receive.

Amanda Pritchard, the chief executive of NHS England is among a number of health heads wishing King Charles well.

"Finding out you have cancer can be very daunting - we hope King Charles’ treatment goes well," she posted to social media, adding a public reminder to get checked if symptoms appear.

King Charles is the patron of Macmillan Cancer Support, and CEO Gemma Peters said: "We'll be there for him every step, as he has been for us since he became our patron in 1997."

Maggie's cancer support chief executive Dame Laura Lee also offered her well wishes, saying: "We are incredibly sorry to hear the King's news and our thoughts are with him. We also know how challenging and worrying a time a cancer diagnosis can be for the whole family and our thoughts are very much with our president [Queen Camilla]."

Sean Coughlan
BBC News royal correspondent

Image source, PA Media

This news of the cancer diagnosis came as a shock, as it was only yesterday that King Charles was seen in public, appearing to be on the mend, waving to crowds in Sandringham.

It's been a bleak start of the year so far for the Royal Family, with the Princess of Wales still facing a long recovery from her abdominal surgery.

Prince William had been expected to spend more time with her and their children, but now he’s going to be picking up the baton for his father, who will be stepping back from public engagements.

As with the news about Catherine’s operation, the news about the King is a mix of modern openness and also a traditional sense of privacy.

The Palace has got ahead of any speculation by revealing the cancer diagnosis, but there is still a great deal that remains unknown about what exactly has been discovered.

But such moments can bring people together and the King personally shared the news with his sons, including talking to Prince Harry in California, with the prince set to visit his father in the coming days.