The strict secret Kate Middleton had to keep after Prince George’s birth

It was a royal birth fit for a queen — and only the queen.

When Kate Middleton and Prince William welcomed Prince George a decade ago, there was one royal rule the couple reportedly had to follow.

According to The Daily Express, the late Queen Elizabeth II was the first in the family to learn that George had arrived in 2013 due to royal protocol, as the reigning monarch is “always notified first.”

The queen passed away in September at the age of 96, after a 70-year reign.

George, meanwhile, celebrated his 10th birthday on Saturday.

William reportedly delivered the news of his birth to the queen with a specially encrypted phone — before the couple could tell their own friends and other family members.

William and Middleton, both 41, had to make sure the queen liked the prince’s name, as she had to approve it, The Daily Express reported.

Prince George Alexander Louis was born at 4:24 p.m. on July 22, 2013, at St. Mary’s Hospital in Paddington, London.

The Post reached out to Kensington Palace for comment.

Even though he just turned 10, George reportedly already knows that he will be king someday.

He is second in line for the throne, after William.

Royal biographer Robert Lacey wrote in his book “Battle of Brothers” that George learned of his future role in the summer of 2020, around his 7th birthday, per the Daily Mail.

Speaking to People recently, one unidentified palace insider claimed that his parents are “making George aware” of his future duties in “the best way they can,” which includes making sure that it’s not all too “burdensome.”

“It’s a massive balancing act,” one royal source recently divulged to the outlet. “William and Kate are doing the right thing, protecting him so he can have as normal a childhood as possible, but he’s also dipping into duties as a future monarch.”

In honor of the tween’s birthday, the Prince and Princess of Wales released a new official portrait of George on their verified Instagram page.

The sweet pic showed George beaming in a button-down shirt and teal pants as he sat on stone steps.

“10 today!” the caption read. “Wishing Prince George a very happy birthday! ????”

And though it’s unclear how Middleton and William celebrated their son on his milestone birthday, it’s safe to assume that Middleton probably baked him a cake.

In 2019, Middleton revealed that she likes to bake her own cakes for her children on their birthdays and typically stays up until midnight to do so.

“I love making the cake,” she admitted in the 2019 BBC Christmas special “A Berry Royal Christmas,” where she paired with expert baker Mary Berry to prepare festive foods for charity workers.

“It’s become a bit of a tradition that I stay up until midnight with ridiculous amounts of cake mix and icing and I make far too much,” Middleton said at the time. “But I love it.”