Queen Camilla and the King shared an image previously posted by William and Catherine

King Charles and Queen Camilla were the first to mark Prince George's 13th birthday with a public tribute on social media this morning.

The King and Queen posted a message on the official Royal Family accounts reading: "Happy Birthday to Prince George!" accompanied by a cake emoji.

Their Majesties also reshared the new portrait that the Prince and Princess of Wales had released of their eldest child to celebrate the occasion.

William and Catherine published the image earlier today with a simple caption: "Happy 13th Birthday, George!"

The photograph, taken by Matt Porteous following last month's Trooping the Colour ceremony, captures the young prince as he becomes a teenager while standing second in line to the throne behind his father.

This year's portrait continues a well-established tradition in which each of George's birthdays has been marked by carefully selected imagery, whether shot by Catherine herself or by chosen professional photographers.

Mr Porteous captured the image shortly after the Trooping the Colour parade, which took place last month.

Since George's birth, the couple have used these annual releases as a way of offering the public a controlled glimpse into their son's life as he grows up in the spotlight.

The progression from royal infant to teenager has been documented through these portraits, with each year's photograph closely watched by the public given George's position in the line of succession.

Today's release follows that same deliberate approach, balancing visibility with the family's desire for privacy.

The couple's approach to parenthood has been shaped by a determination to shield their children from the pressures of royal life.

A source told the Telegraph that William and Catherine have been "relentlessly focused" on this challenge since before George's arrival.

"No one knows better than William what life is like growing up in the Royal family," the source says. "He is absolutely determined to get it right."

Those in their circle describe a philosophy that places family above institutional demands. "They will serve the institution, but they will also make sure their children are raised with as much normality as possible," says a friend.

That commitment extends to everyday parenting; the couple participate in school WhatsApp groups, organise play dates and manage the school run themselves.

At Lambrook Prep School in Berkshire, George and his siblings Charlotte and Louis have been fully immersed in school life, from extracurricular activities to trips away. William and Catherine have equally thrown themselves into the parental side, attending sports fixtures, chapel services and other school events.

"The way they have lived their lives getting the kids outside, spending time together, focusing on the school run - it's just as strategic as any other part of their public service," a source said.

Recent months have brought signs of George's increasing independence. "George was boarding last night," William remarked during a radio interview this summer.

Come September, the young prince will start at Eton, joining the same boarding house where both his father and uncle previously lived. He will be accompanied by friends from Lambrook and acquaintances from the prep-school sporting circuit.