BY the age of 73, it could be argued the new King has already completed, as Prince of Wales, a career of duty and service of such length he should be looking forward to a few years of well-earned rest.
Yet he has just begun what is his greatest challenge.
Not, as some have suggested, the role he has been waiting for all his life — rather the job he was ready to do when the time came.
Nothing has been left to chance — all the long-established succession plans will now be put into action.
The royal household is organised along military lines, with plans agreed months in advance by a close-knit team of advisers and staff.
Accordingly, the new king’s life will be plotted hour by hour, as it has been since he was a young man.
Read More On The Queen's Death
It means that no matter where he is, the King’s life can continue with maximum efficiency and minimum disruption.
His household is run with precision by a small but dedicated team of staff, most of whom have been with him for decades.
They are some of the most loyal, kind and funny people I have ever met.
The working day is pretty relentless.
Beginning with the radio news headlines and a breakfast of seasonal fruit salad and seeds with tea.
Despite rumours that the King is served a line of eggs to choose from every morning, I never saw a single boiled egg at breakfast in all the years I worked there.
Public engagements start shortly afterwards and run through until 5pm.
The King doesn’t eat lunch — so, an early lesson I learnt when out on the road with him was to have a big breakfast or bring a few snack bars to keep you going.
It comes as…
In a typical year as Prince of Wales he would complete about 500 engagements, some 200 jointly with the Duchess of Cornwall, visiting most UK counties along the way.
The overseas tours would be similarly packed with a mix of nation and state work — laying wreaths and meeting national leaders — alongside events focused on his charitable interests.
Throughout these visits, the thing that struck me was how interested the King is in everything and everyone he meets.
Because of this, his conversations almost always overran.
I frequently saw people try to impress him with their intellectual prowess or social standing, to little effect.
He doesn’t draw a distinction between the well-heeled and those who have the toughest of lives.
He’s interested in people, not position.
I remember when we went to visit the set of the 25th Bond film, No Time To Die.
I was looking forward to him meeting Daniel Craig and the rest of the cast.
But as we approached, he kept stopping to speak to the set designers, the security guards and just about everyone else.
Each person, star or not, was treated with exactly the same courtesy.
A day in the office is equally busy.
Back-to-back 45-minute sessions — on his charity’s next project, a forthcoming tour or a discussion with Sir Clive Alderton, his principal private secretary, about matters of state.
The vast array of topics covered in a single day reflects his polymath mindset and can be difficult to keep on top of.
The one thing you were always advised to do was make copious notes in case you forgot the detail: he certainly never does.
He has an incredibly sharp memory.
About 1pm there would usually be a break — not to eat but to get outside to walk.
The King dislikes being inside for too long and always has the windows wide open.
A meeting at Birkhall, his home in the Highlands, in the middle of winter was not for the faint-hearted.
I can remember more than one occasion when I thought I might have actually got frostbite while trying to write with a hand I could no longer feel.
The King is a convener, connecting people and organisations in ways that open up possibilities and create solutions.
He approaches problem-solving in a more instinctive, fluid way.
Whether it was knife crime or ways to reduce the carbon footprint of the aviation industry, he would invite the best brains and the most experienced people in to listen to their ideas and advice.
And the fascinating thing was that everyone was happy to help.
I suspect it is a modus operandi that will continue in this new role.
The first real pause in the day will be at 5pm, when the King will stop for tea — a chance for him to recharge, often with the Queen Consort, over sandwiches and a piece of fruit cake.
If there is anything left after the cake has been passed around, it will be placed in a Tupperware box to reappear the next day and the day after that.
Then it’s back to his desk to tackle the mountain of paperwork.
Dinner is at 8.30pm sharp and then at 10pm he heads back to his desk, usually until well past midnight.
It wasn’t just the desk time that would last way beyond the nine-to-five working day.
Public engagements extend well into the evening.
When I asked what drove him to get involved with so many issues, he said he felt it was important to use his position in the best way possible.
He knew he’d be accused of meddling . . . and was when the “black spider memos” — a cache of correspondence between him and government ministers and so-called because of his handwriting — were published in 2015.
All it showed was that the King was passing on information given to him by the public and organisations.
He certainly didn’t expect ministers to act on his every word but he did feel they might appreciate knowing what the public was saying to him.
“If that’s meddling, then I am very proud of it,” he once said.
The King now begins his new role with the support of the Queen Consort at his side.
Read More on The Sun
For him, “moving up one” will be a perfectly natural transition.
From the campaigning prince to the convening King — to be consulted, to advise and to warn, just as his mother did before him.
