The Prince and Princess of Wales' children came out to celebrate their grandfather's official birthday today, Saturday, June 17.
Prince George, nine, Princess Charlotte, eight, and Prince Louis, five, were beaming and waving at the crowds during their carriage ride at The King's Trooping the Colour parade.
On first glance it might have looked like Prince George and Louis were in identical outfits - navy suits and red ties - but eagle eyed onlookers will have noticed one key difference. Prince Louis was wearing bright red shorts - a look he's become known for.
Royal fans were quick to notice Louis' signature outfit, with one person noting: "Prince Louis' wee red shorts! Stop it. I can't handle the cute!"
Although it might not seem strange that the young royal is wearing shorts on a day like today, which comes off the back of a scorching heatwave, but Louis actually wears them whatever weather.
Usually, as was the case today, you'll see his brother George sporting smart trousers – but why?
According to etiquette expert William Hanson, the reason behind the Duke and Duchess of Cambridge's outfit choices is tradition - and essentially because they are quite posh.
Speaking to Harper's Bazaar, he explained that the tradition dates back to the 16th century, saying: "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.
"Although times are slowly changing, a pair of trousers on a young boy is considered quite middle class – quite suburban. And no self-respecting aristo or royal would want to be considered suburban. Even the Duchess of Cambridge."
When George was younger, he could often be seen wearing shorts, as did Prince William and Prince Harry in their time.
According to Hanson, boys usually switch to trousers when they are eight, which is no doubt why George is wearing his smart trousers for the Trooping of the Colour celebration.
No doubt it means that Prince Louis has a few years of short wearing left until he can graduate to big boy trousers.
