The prime minister spoke to BBC Radio 5 Live's Rachel Burden this morning.

Emma Vardy
Reporting from Santa Barbara, California

Image source, Reuters

Prince Harry is expected to arrive in the UK today after his car was reportedly seen at Los Angeles' main airport, known as LAX.

Soon after Buckingham Palace’s announcement on Monday, Prince Harry's team said he would travel to the UK to see his father, while his wife Meghan will stay in California with their two children.

Now Harry is believed to be on a flight to the UK - which should take around 11 hours.

While Harry’s relationship with his family has been strained since he moved to the US, he continues to have a bond with his father.

Simon Lewis, the Queen's former press secretary, says Buckingham Palace's statement on Monday evening was "spot on".

Even 20 years ago, all we would have received was a "very abrupt, short statement", he says.

And - even though the type of cancer hasn't been revealed - the Palace went as far as possible, Lewis tells the Today programme.

"The most important point", Lewis adds, was the Palace confirming the King would continue his state duties and paperwork.

US President Joe Biden says navigating a cancer diagnosis “takes hope and absolute courage,” adding that he and his wife are praying for Charles’s swift recovery - watch more of his comments below.

Indian Prime Minister Narendra Modi wishes a “speedy recovery and good health” to the King, while French President Emmanuel Macron says his thoughts are with the British people.

The world's media has also been reacting to the news, which broke at 18:00 GMT on Monday.

France’s Le Monde says the diagnosis “poses a concrete problem to the Royal Family and by extension the monarchy: there are no longer many royals available to appear in public”.

Germany’s Der Spiegel, meanwhile, says "the Windsors are made of tough stuff" - pointing out that Queen Elizabeth II lived to 96 and Charles’s father Philip to 99.

Robert Hardman, a Royal Family journalist and filmmaker, says there is "a fairly upbeat approach" from Buckingham Palace after the King's diagnosis.

Hardman tells BBC Radio 4's Today programme the announcement reminds him of the early days of Covid, when people asked how such a public-facing institution would survive the pandemic.

But they found new ways of operating, Hardman says, and managed "very well".

The King may resort to Zoom meetings, he says, like the Queen did during the pandemic. That in some ways brought her closer to the public, Hardman says, as clips of her meetings were shared.

Hardman adds there will be moments when King Charles's absence will be noted - possibly on Commonwealth Day in March - but the "day-to-day running of monarchy will not really change".

Age is the top risk factor for cancerpublished at 07:50 Greenwich Mean Time 6 February

07:50 GMT 6 February

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.

Prime Minister Rishi Sunak confirms that he remains in "regular contact" with King Charles and that he intends to "crack on like normal".

"All our thoughts are with him and his family," Sunak says, adding: "I’m in regular contact as I always am."

Prime Minister Rishi Sunak says he is "shocked and sad" to hear of King Charles's cancer diagnosis.

He says he is thankful the illness was "caught early", and hopes the monarch makes a speedy recovery.

Image source, PA Media

We're expecting Prime Minister Rishi Sunak on BBC Radio 5 Live soon - he's mainly talking about the final cost of living payments, but we're also expecting a question on the King's health.

Listen here, or stay on this page for the latest lines.

Emma Vardy
Reporting from Montecito, California

Image source, Getty Images

As we just reported, Prince Harry is due to arrive in the UK "in the coming days", after the King told his son personally of his cancer diagnosis.

In Montecito - the prince's picturesque home town, where his wife and children will remain - there are soggy palm trees and sandbags keeping floodwaters out, as California is hit by a devastating storm.

Locals here tell us Harry and Meghan are sometimes spotted around the area, on school runs or going to the gym.

But they live in a very exclusive gated community - and VIPs are not unusual in Montecito, so their comings and goings are very private.

The news of the King's cancer diagnosis is being reported widely on US networks. There is a lot of interest and affection for the royals here.

The King will continue his key constitutional rolepublished at 07:01 Greenwich Mean Time 6 February

07:01 GMT 6 February

Chris Mason
Political editor

Image source, Getty Images

When you examine the wiring of the British state, the core connections lie between monarch and government, between Buckingham Palace and Westminster.

While we are told we will see less of the King in public while he receives cancer treatment, much of his private work will continue.

He will continue to receive his red boxes, the daily exchange of paperwork at the heart of his role.

Take - as just one example - the passage of a law at Westminster.

After it has passed through all its stages in the House of Commons and the House of Lords, it heads to the Palace for what is known as Royal Assent.

A formality, yes, in a parliamentary democracy, but an illustration of the King's key constitutional role.

Another example, again a formality, when the prime minister appoints a new minister, it is technically a Crown appointment - an appointment made by the King.

We understand the King's weekly audiences with Rishi Sunak - a long-standing convention going back decades and hugely appreciated by prime ministers - will continue.

Image source, Reuters

Last night, Prince Harry's team confirmed he will fly to London to see his father. The King told his family personally of his diagnosis, the Palace says.

We don't know when Harry will arrive in the UK, but he is due to leave California "in the coming days".

The Prince is expected to arrive in London on his own. His wife Meghan will remain in the United States with the couple's two children - Prince Archie and Princess Lilibet.

Harry's visit has raised hopes of a reconciliation within the Royal Family, amid the Duke and Duchess of Sussex's troubled relationship with King Charles and Prince William.

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 could no longer be called upon as they are non-working royals.

News of the King's diagnosis dominates Tuesday's front pages.

"King: I have cancer", is the Sun's headline. The Mirror calls the King's diagnosis a "shock", and reports that it was his recent prostate operation which led to the diagnosis.

The Times reports that Buckingham Palace says Charles is "wholly positive" about his treatment. The i says that the announcement "abandons royal protocol" regarding comment on the monarch's health.

The Express says Prince Harry will fly to the UK to see his father in the coming days.

The King's treatment will keep him from public-facing engagements, but he will continue with his constitutional role as head of state, the Guardian reports.

The Telegraph devoted its entire front page to the story. The paper reports that Charles was last seen attending a church service on Sunday, where he looked "weary, but smiled and waved to the public".

The Daily Mail says Charles's condition has been caught early and that the prognosis is good.

• You can read the full paper review here

• 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"

Here's what Buckingham Palace said in its announcement yesterday - you can also read the full thing here.

Alex Binley
Live reporter

Good morning and welcome to our coverage following the news of King Charles's cancer diagnosis.

Here's the latest on what we know:

• King Charles spent the night at home in London after beginning out-patient cancer treatment

• Buckingham Palace announced the King's condition on Monday - but hasn't revealed what kind of cancer he has. However, officials say it isn't prostate cancer
• It was discovered while the King was in hospital receiving treatment for a benign enlarged prostate

• In a statement - which you can read in full here - the Palace said the King had begun regular treatment
• He will postpone public duties, although he's still expected to continue with paperwork and private meetings, the Palace confirmed

• Prince William is expected to cover some engagements on the King's behalf

• 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
• Politicians, religious leaders and celebrities have been 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

We'll be bringing you the latest developments here, so stay with us.