Ever year for Trooping the Colour, thousands of royal enthusiasts line the streets of London, and a lucky few who are chosen via an online ballot, gain VIP access inside the Horse Guards Parade to watch the main event.
It's another occasion where sartorial fanatics eagerly await to see what our stylish royals step out in. Last year the Princess of Wales, stunned in a striking green coat dress by Singapore-born designer Andrew GN, a Philip Treacy hat and the late Princess Diana's sapphire earrings
Granted, royals step out in their Sunday (well, Saturday) best for the occasion each year. But do onlookers need to adhere to a dress code? And what do those inside the Horse Guards Palace need to wear? Here's everything you need to know...
What is Trooping the Colour?
Trooping the Colour is the annual celebration held to mark the reigning sovereign's birthday.
"Over 1400 parading soldiers, 200 horses and 400 musicians come together each June in a great display of military precision, horsemanship and fanfare," explains the Royal Family's website.
"The streets are lined with crowds waving flags as the parade moves from Buckingham Palace and down The Mall to Horse Guard's Parade, alongside members of the Royal Family on horseback and in carriages."
The celebrations close with iconic RAF fly past, where 9 Air Force plans fly over creating the colours of the Union Jack, and the Royal Family waves from Buckingham Palace's famous balcony.
What is the Trooping the Colour dress code?
There is no official dress code for those who line the streets to catch a glimpse of the festivities, but those who secured tickets for the official event must adhere to the sartorial requirements.
The official website explains: "This is a formal State Ceremonial Parade in the presence of His Majesty The King. Those attending are required to dress accordingly".
"Morning dress; lounge suit; or jacket, tie & trousers for gentlemen / equivalent for ladies. Children must also be dressed smartly."
For those unsure what morning dress is, it's the very British way of saying the traditional attire worn by men predominately at daytime events in the presence of The King and at some events during the social season, notably, Royal Ascot.
The ensemble includes the usual shirt, trousers and waistcoat, but what sets it apart from the typical suit, is the morning coat - a blazer-style overcoat with peak lapels and tails that fall to around knee length.
A top hat is also a typical component of morning dressing but isn't essential for Trooping the Colour. However, official guidelines say they are "recommended for paying compliments to His Majesty and the Colours as they pass."
For ladies, we'd suggest opting for dresses that are maxi or fall just below the knee to be safe, and smart flat shoes or heels. Think of the dress code as the Royal Enclosure at Ascot, without the absolute necessity of a headpiece. But If you did want to wear a headpiece, use these stylish Ascot hats as inspo.
Sandals, denim, trainers, t-shirts and flipflops are forbidden.
Though the stylish Princess of Wales will be missed this year, we can't wait to see what notable royals and VIP guests wear this June...