Prince Louis’ birthday photos all have this in common – did you notice?

Prince William and Princess Kate’s youngest son, Prince Louis, celebrated his sixth birthday yesterday, with the royals sharing a photo of him to mark the day.

The sweet snap shows the young prince lying on the ground smiling for the camera, in a picture taken by his mother, the Princess of Wales. The photo mirrors Louis’ previous birthday portraits in that it was taken outside – but did you notice the other similarity between his birthday posts?

Eagle-eyed royal watchers who have been following Louis’ life will have noticed that each and every one of Louis’ birthday photos shows the youngster wearing a smart shirt. In his first birthday snap, Louis wears a round collared shirt with a red trim, while for his second birthday, Princess Kate dressed him in a blue and white gingham number.

By the time his third birthday rolled around, Louis was trussed up in a blue and white striped shirt under a cosy navy jumper, and for his fourth birthday, he wore a check shirt under a star print pullover.