The harsh rule that Prince Louis has to follow but Prince George and Charlotte don't

There is a harsh rule that Prince Louis has to follow, but Prince George, Princess Charlotte, and some of his other royal cousins are exempt.

• Prince Louis is the youngest son of Prince William and the Duchess of Cambridge.
• Due to his place in the royal line of succession, the young royal must follow outdated fashion rules that don't apply to his other family members.
• In other royal news, Mike Tindall celebrates the Queen's 70-year reign with cheeky tribute.

There are plenty of royal protocols that the royals must abide by, and there are plenty of strange ones that apply just to the youngest members of the royal family.

Although Prince Louis is just 3 years old, there is a tricky rule that he must keep to when it comes to his clothing. Reportedly, young boys in the royal family are not permitted to wear trousers at royal engagements and must instead wear shorts. 

While this isn't typically a problem, this can be an issue when the weather is colder in the UK, and the young boys in the family are still expected to keep their knees bare.

William Hanson, an etiquette expert, explained the custom to Harper's Bazaar. 

"It's a very English thing to dress a young boy in shorts. Trousers are for older boys and men, whereas shorts on young boys is one of those silent class markers that we have in England." explained the expert. 

"Although times are (slowly) changing, a pair of trousers on a young boy is considered quite middle class—quite suburban."

Sadly for Louis, this is also a rule that he must follow on his own. His older brother Prince George is 8, meaning that he is no longer expected to dress in shorts and can wear long trousers which is a more sensible choice for an older child.

This rule only applies to boys in the royal family, so Princess Charlotte has been able to avoid this entirely. This also applies to the other young royals in the family including Princess Beatrice's daughter who's name is a sweet nod to the Queen. 

The first photo of Lilibet Diana showed that Prince Harry and Meghan have decided to ignore this royal protocol when it comes to dressing their son Archie. In the image,   Archie, who will be 3 in a few months, wore full-length jeans that covered his knees.

It is unclear if any other of the Queen's great-grandchildren will be forced to wear shorts in public, as Zara's son Lucas and Princess Eugenie's son August are not yet at toddler age and are both more sheltered from public life as a member of the royal family.