It was an announcement that sent shockwaves around the world – King Charles had cancer and would be stepping back from public-facing duty just 16 months into his reign.

For this no-nonsense, keep-calm and-carry-on Monarch — eldest son of the even more hard-headed Prince Philip — to admit he had to ease back on his workload meant one thing: it was bad.

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King Charles attending the Mey Highland Games in ScotlandCredit: Getty

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The King leaving church in Sandringham with CamillaCredit: Paul Edwards
Dutiful Camilla, 77, stood in for the King when he stepped back from a string of engagements including the Royal Maundy Service at Worcester Cathedral and a solo two-day visit to Belfast, both in March.

But fast forward just six months from the announcement and incredibly he is now fit enough to travel 10,000 miles for a gruelling tour of Australia and Samoa.

As one source close to the King, 75, told me: “The sun wasn’t shining in February but it is shining now”.

The King’s aides were keen to point out when he made his public comeback at a cancer hospital on April 30 that not all recovery programmes for cancer patients are the same.

Yet while he is “not yet out of the woods”, according to those in his inner circle, they add there is “great optimism” and treatment has gone “better than anyone would have thought”.

Today the details of exactly how the Royal Household put our much-loved Monarch back together again are revealed.

From exactly why he was pulled from duty to the pioneering treatments that meant he never lost his hair — and the real reason his wayward son, Harry, was given an audience of just 30 minutes.

Charles’ ordeal began in January when he revealed he needed a corrective procedure for an enlarged prostate.

He decided to allow the public to know what he was going through, which resulted in a huge outpouring of sympathy.

Charles was touched by the public reaction but also significantly buoyed when it was revealed the NHS website received 11 times more daily visits from men with similar concerns.

But then his condition would take a turn for the worse.

Charles was due to spend two nights in the London Clinic — where Kate was also being treated — so when he spent a third night in care, people started to become concerned.

Those worries were realised when tests revealed cancer.

But rather than hide this devastating news from the public he decided that following the supportive reaction to his prostate diagnosis he would allow it to be made public.

Weekly treatment

A carefully constructed plan inspired by Operation Bubble which protected the late Queen from Covid-19 was thrown into action.

He would have weekly treatment in London and factor in vital periods of rest time at Sandringham, Highgrove and Windsor.

But his health plan was thrown into turmoil when Prince Harry announced he would jet from Los Angeles to see his father.

While the King delayed his helicopter flight from Buckingham Palace to Sandringham, his wayward son was given just 30 minutes of his company at Clarence House.

Plans were in place to avoid the King contacting a secondary infection and Harry flying 5,000 miles on a jet was not ideal.

Aides prevented Harry, 39, joining his father at Sandringham fearing “we’d never get rid of him” and he needed to reduce his social contact while undergoing cancer treatment.

During this time a Freedom of Information request revealed the Department for Culture and Media had begun procurement for the King’s potential funeral — although sources say this is not unusual.

Suggestions that William had been lined up as a potential Prince Regent if the King was unable to carry out the position have been denied by Buckingham Palace.

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King Charles leaving Clarence House on March 28thCredit: Peter Jordan

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King Charles wearing his crown at the state opening of ParliamentCredit: AFP
But the King was withdrawn from all public duty for 103 days although he continued reading government red boxes.

It can now be revealed the decision to postpone his public facing role was made as a “precautionary measure” because of the King’s diminished immune response to other diseases.

The Royal Household copied Covid-style protocols — or tiers imposed by the Government during the pandemic — to minimise secondary infection such as seasonal cold or flu.

A source said: “We had to minimise potential risk from other people, not because he couldn’t do the job.”

But as winter turned into spring and weather became warmer it meant they could relax the Covid-style tiers.

This was demonstrated when the King emerged from the Easter Sunday service and was greeted by 60 well-wishers at St George’s Chapel, Windsor Castle.

Just days earlier, the monarch and his team had received news that the treatment had gone better than anyone could have expected.

One insider said: “He was raring to go after the positive results and didn’t want to hang around any longer”.

Covid-style tiers

It meant the King told aides that a trip to Australia, seen as the most important tour a monarch will ever take, must go ahead in the autumn, as first revealed by The Sun.

In May, his public comeback began at London’s University College Hospital MacMillan Cancer Centre where he told patients he was having treatment later that day and confessed in an off-script moment he had lost his sense of taste.

But Covid-style tiers remained in place and he was restricted to the amount of people he could be with.

A similar “tier” achieved was attending D-Day commemorations in June when the King had treatment the day before the Portsmouth ceremony.

He then travelled to France but avoided the gathering of world leaders because the event often overran by several hours and instead attended a short service with British D-Day veterans.

A source said: “It wasn’t like he was totally broken and nor are we totally out of the woods yet as treatment continues.

“Treatment has gone better than anyone would have thought even in their most optimistic thoughts.”

Such was the progress that the King was now able to host around 50 people indoors at places including Buckingham Palace.

A Prince’s Trust bash there on May 22, the day of the general election announcement, was one event where numbers of guests had to be kept low.

At some events in Jersey and Guernsey in July he met as many as a 100.

But he still managed to carry out 464 engagements in a year and more than 105,000 invited guests had walked through the doors of Royal palaces.

There has often been a suggestion the King could be “grumpy” but a source added: “When battling illness, what he has been able to do gives him a sense of great positivity and encouragement.

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King Charles in military dress at a D-Day ceremonyCredit: AFP

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The King with Maya Jama, at a Buckingham Palace partyCredit: PA
“Having a great positive frame of mind is as important as having the best medical expertise for the physical side of his symptoms.

“It’s been a great boost for morale and recovery that he is able to complete the scale and nature of events he is able to undertake.”

Around 27,000 messages and get well soon cards had been sent to the King and Princess of Wales, and he told then-Prime Minister Rishi Sunak some of the “wonderful messages and cards” have “reduced me to tears”.

Despite the King’s positivity and drive to return to work and tour Australia, his aides and doctors remain “protective” about how many hours a day he can carry out public-facing duties.

While famous for being a “workaholic” with Harry and William once saying they would find him in his office working during the night, the King has been made to restrict public face-to-face interaction to only five hours a day.

This is expected to be the same when he goes to Australia with Camilla in October where the tour is expected to have engagements on around seven days.

Sources explain rest and recuperation are built into the King’s usually hectic schedule so he is not exhausted.

One explained: “Rest and recovery has to be taken as seriously a priority as government duty, public duty, so we build in rest periods and try to limit the number of hours a day that are public-facing duties.”

But, this has not meant he has stopped working outside the five hours of public roles. One said: “In terms of getting through red boxes people assume it takes longer, but it’s quite the opposite, it has brought him more time at his desk which he loves.”

After his enlarged prostate diagnosis in January The Sun revealed Camilla had urged Charles to “slow down”.

And backed by his wife, the King has agreed to have at least a light snack at lunchtimes after spending his whole life skipping the meal.

He even visited Balmoral the night before the castle opened to tourists for the first time this summer.

And, in July, he was seen marching up and down the corridors at Buckingham Palace to check everything was in the right place ahead of the East Wing opening to visitors.

But of course the major reason the King is making a speedy recovery is the “pioneering non-intrusive treatment” which is continuing.

Experts explain that in the past two or three years there has been a “transformation” and “quiet revolution” in cancer treatment for all patients.

When previously, there would be a “Blitzkrieg” approach to treating cancer the disease is now hit with “precision guided weapons”, sources close to the treatment explained.

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King Charles with Camilla in St Peter Port, GuernseyCredit: AFP

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The King meeting patients at University College Hospital Macmillan Cancer CentreCredit: AFP
It has been noted by those close to the King that he has not suffered any notable hair loss.

Losing his hair was a natural concern for the King, even if he is thinning on top.

And a further boost for the King is the treatment has not resulted in any particularly debilitating side effects.

A source said: “He is not pioneering in any way as it’s available for any cancer patient.

“The treatments are highly evolved and sophisticated in ways previous treatments were not.”

But one downside was the King was prevented from appearing at Trooping the Colour birthday celebrations in June on his horse Noble who was instead ridden by Princess Anne.

‘Genuinely bowled over’

Claims the King was “furious” and “felt it was a failure” have been downplayed by the Palace who insist he “accepted the reality of the situation”.

In truth, if it was not the cancer then the prostate procedure would have stopped him riding at Trooping, it is said.

Amid the recovery his personal doctor Michael Dixon, previously slated and accused of backing controversial homeopathy, has been credited with aiding his recovery with a programme of complementary treatment.

The King will now spend summer months at Birkhall on the Balmoral estate and be surrounded by family, including the Princess of Wales who is continuing her own cancer journey.

He will keep a positive frame of mind tending his garden, taking long walks, painting and fishing.

And he will be ready and raring to go for Australia in October where his recovery could be even further down the line.

The trip Down Under which includes speaking at Common wealth Heads of Government Meeting in Samoa is expected to last less than two weeks including travel and take in Sydney and Canberra

The King has been open about his prostate problem and cancer but it is unlikely he will now specifically name which cancer he has, so that to “reach out and embrace as many people as he can impacted by cancer. The more specific you are the fewer people you are able to engage and support.”

Of making the news public, an insider said: “I can’t tell you what a difference that has made for him, it came with his support.

“When presented with facts of how many suffered enlarged prostate, and that there was a public health campaign and therefore some good can come of his personal setback, he totally got that and has been genuinely bowled over by the scale of response to that and cancer itself.”

On social channels, Buckingham Palace has collaborated with charities MacMillan, Maggie’s and Cancer Research UK.

And when the King chose his comeback event, he attended University Hospitals cancer ward where he bonded with patients revealing he had lost his sense of taste and had treatment later that day.

But a source added: “Never say never. There are no current plans to reveal the cancer.

“But if he felt that the time was right . . . ”

The King began his reign with the “Four Cs” which were Commonwealth, Climate, Culture and Community.

He has added a fifth C in cancer but it is not set to define his reign.