To a select group, King Charles III is simply 'Grandpa Wales'

The King, Queen wave from Buckingham balcony King Charles III and Queen Camilla wave to supports from the balcony of Buckingham Palace.

To the world, he is "King Charles" or "Your Majesty." But to a very select group he is simply "Grandpa Wales."

The King has five grandchildren. The oldest is Prince George who was born in 2013. To mark the moment, Charles planted a tree in his honour at Balmoral, the Royal Family’s Scottish estate.

Now nine years old, Prince George is third in line to the throne and will make history on Saturday when he is a Page of Honour. He will be the youngest of the four pages who will help carry the King’s robes.

"Prince George is gradually learning how to behave in public, whether it’s a football match or whether it’s a family event or a state event," said Royal expert Angela Levin. "He’s beginning to learn what’s expected of him."

The son of Prince William will be the first heir to the throne to take part in a coronation.

Queen Camilla will have her own four pages that day. She has chosen her three grandsons, Gus and Louis Lopes and Freddy Parker Bowles, and her great-nephew, Arthur Elliot.

It seems clear that Charles does enjoy the time he spends as "Grandpa Wales." He is often photographed having a laugh with Prince Louis, Prince William’s youngest son.

"King Charles loves his grandchildren," said royal expert Angela Levin, "and is very sort of playful with them… I think the most touching thing we’ve seen is Prince Charles and Prince Louis, the youngest one (of Prince William’s children) is always seen hugging his grandfather."

Prince William agrees, saying in a recent BBC documentary that the King is a “brilliant” grandfather. But he adds he “would like him to have more time with the children.” But that’s unlikely. Even as Prince, he was a known workaholic. His second son, Prince Harry, once said, “This is a man… (who) will fall asleep on his notes — to the point where he’ll wake up with a piece of paper stuck to his face!”

Now, with even greater royal responsibilities, the King will have even less free time. That time is already limited with his two youngest grandchildren, but not because of his job. Prince Archie and Princess Lilibet live with Prince Harry and his wife Meghan in California.

"He can’t really connect to them because I think they’ve seen them twice, just for a few minutes," Levin said. "I think it’s very sad for King Charles." And there won’t be a reunion this weekend because the children aren’t coming to London for the Coronation. Prince Harry is travelling on his own.

The King has rarely spoken publicly about being a grandfather. When he does, it’s connected to a cause close to his heart, climate change.

It’s clear he had the future generation on his mind when giving a recent speech, saying, “I worry about your grandchildren and everybody’s grandchildren as well as my own. And it just seemed to me that I couldn’t possibly face my grandchildren or yours, if at the end of the day, we’ve completely mucked up the whole of our environment."