Royal fans point out hidden detail in Prince Louis' new birthday portrait

Royal fans have pointed out a subtle detail about Prince Louis' recent birthday portrait that you may have missed.

Prince Louis turned seven on Wednesday (23 April), and to mark the special day, the Prince and Princess of Wales released an adorable portrait.

Prince Louis is the youngest son of William and Kate, who are also parents to Princess Charlotte, nine, and Prince George, 11.

While in the photo, Louis looks smart in a check shirt and jumper, some royal fans pointed out something they noticed.

The prince is seen wearing trousers - specifically jeans. Louis has rarely been seen wearing trousers previously, and is often spotted in shorts.

According to HELLO! royal boys wear shorts until they are deemed old enough to wear trousers.

British etiquette coach William Hanson told the publication in 2018: "Today, young boys usually transition into trousers around age seven.

"Prince George is always seen in shorts because upper class and upper middle-class parents believe that little boys should look like little boys, and so try to keep their offspring looking as cute and innocent for as long as possible."

In the photo, people pointed out that Louis is now old enough to have transitioned into trousers.

One person wrote: "Prince Louis growing up. In long trousers (jeans even) and awaiting new front teeth. Terrific photo. Wishing Louis a fun family day, a delicious homemade cake and a great year."

While another said: "Happy Birthday Prince Louis. I like the green jumper. Great to see you in trousers! Wishing you a good day."

Others pointed out how 'grown up' the royal looks, with another adding: "He’s suddenly all grown up. Happy birthday to Prince Louis!!

And a third added: "Wow, so grown up all of a sudden! Happy Birthday Louis."

And a fourth added: "You look so grown up in this photo!! I hope you have a wonderful day today with your beautiful family. God bless you."

In the portrait, Louis can be seen sitting in a woodland setting surrounded by bluebells on top of what looks to be a tree stump, with a huge grin on his face.

It is believed he is sitting in the garden at Anmer Hall in Norfolk, which is the family's residence on the Sandringham Estate.

"Wishing Prince Louis a very Happy 7th Birthday!" the photo is captioned.

Louis was born at 11:01am on 23 April 2018 in St Mary's Hospital in London.

Prince Louis weighed eight pounds seven ounces when he was born, and he and Kate were able to return home to Kensington Palace later that day.