The King reaches the second anniversary of his accession to the throne and the death of Queen Elizabeth II on Sunday, with his health “heading in a very positive trajectory”, a royal source has said.

Charles, 75, became head of state immediately upon the death of his mother, the nation’s longest-reigning monarch, who died peacefully at Balmoral Castle on September 8 2022 at the age of 96.

The King, who is still considered a “newbie monarch” in comparison with his mother’s record-breaking tenure, endured a bombshell second year as sovereign, being diagnosed with cancer, dealing with ongoing treatment, while his daughter-in-law the Princess of Wales was also being treated for the disease.

But a source said Charles had coped with the past year with a “determination to be as public as he was able” to reassure the nation about how much he could still do.

He has also been buoyed by Queen Camilla’s support.

“Her natural warmth, resilience and sense of humour, as I’m sure any patient will tell you, is a wonderful thing to have,” the source told the PA news agency.

“Of course it’s been a stressful year for Her Majesty, too, but there was never a sense of despondency, only a determination that they would get through this, as with so many other challenging issues in the past.”

On Saturday, the King was seen chuckling and appearing to wipe away tears of laughter as he and Camilla watched the annual Braemar Gathering.

The monarch, in a tweed jacket and tartan kilt, and the Queen, wearing a navy dress with a feather pattern and a feathered hat, took front row seats for the traditional Highland Games, a short drive from Balmoral.

Charles is expected to attend church, spending time in private prayers and reflection, on the anniversary, which falls during his summer break on his Aberdeenshire estate in the Scottish Highlands.

The source: “There will be personal thoughts, prayers and reflections.

“I’m sure it will be a very poignant day for all. How could it not be, not least given the year of challenge that the whole family has had?”

The King and Queen are gearing up for an important tour to Australia and Samoa in the autumn – their first major overseas trip since news of Charles’s cancer was announced.

“Health has to remain the number one priority, albeit heading in a very positive trajectory,” the source said.

Camilla gave an insight into the King’s treatment this week when she opened a new cancer centre in Bath, revealing he was “doing very well”.

Down-time will be incorporated in Australia and Samoa, with not too many back to back meetings, consideration given to the time difference, and a hoped-for trip to New Zealand removed to reduce the travel demands, but Charles’s programme is still expected to be “pretty full on”.

The King spent around three months away from public-facing duties and returned in April with a visit to a cancer centre in London.

He had a high profile run of engagements through the next few months with D-Day 80th anniversary commemorations in Portsmouth and Normandy, Trooping the Colour, the incoming Japanese state visit, a short trip to Jersey and Guernsey, the appointment of a new Prime Minister after Labour’s landslide general election, and the State Opening of Parliament.

“The best way of seeing how the King has coped is through his actions and words – everything that you’ve seen, everything that he’s said, and everything that he’s done,” the source said.

“From the earliest outset of the health challenge, it was the King’s determination to be as public as he was able, so that people could be reassured by just how much he was still able to do in the circumstances, under his doctors’ advice.

“That has obviously slowly dialed up as the program of treatment and recovery continued, with the result that the King is off on a 12,000 mile trip to Australia and Samoa in a few weeks’ time.”

The third year of his reign will see a continuation of his so-called “4Cs” – his guiding principles of “culture, Commonwealth, community and climate” – with an additional sideline theme of “cancer”.

The King is said to have been greatly encouraged by the way his personal health has been able to broaden discussion and engagement around the issues of all forms of cancer, such as the rise in prostate screening after he had surgery at the start of the year.

He hopes to be able to show how people diagnosed with cancer can, if it is right for them, carry on with as much of their normal lives as possible.

The King has been enjoying his summer break, and looked happy and relaxed when he attended the Aberdeen flower show last Saturday.

Gun salutes are usually fired on Accession Day, but because this year the anniversary falls on a Sunday when salutes traditionally do not take place, the military tribute by The King’s Troop Royal Horse Artillery at Hyde Park and The Honourable Artillery Company at the Tower of London has been moved to Monday.

Both regiments taking part were responsible for firing the Death Gun salutes to mark the death of Queen Elizabeth II two years ago, with almost all of the soldiers and horses taking part playing a part in the Queen’s state funeral and the proclamation of the King.