It's one of the most glamorous events of the summer that brings together the Royal Family, fashion and, of course, horse racing.
Royal Ascot has kicked off for another year with King Charles and Queen Camilla leading the charge of members of the Firm, who attend the event much loved by the late Queen.
Over the course of the five-day race meeting, most royals are expected to attend including the likes of the Prince and Princess of Wales, Duke and Duchess of Edinburgh and racing lovers Zara and Mike Tindall.
When attending, they always look the picture of perfection, with gorgeous dresses, stunning hats or smart morning suits.
And this is because to gain entry to the Royal Enclosure at Ascot race course, a strict dress code must be adhered to at all times.
So what dress rules do the royals and others lucky enough to have a ticket to the Royal Enclosure must they follow? Here we take a look...
Female dress code
When it comes to ladies at Royal Ascot in the Royal Enclosure - the dress code is described as "formal daywear" with a number of strict rules.
Most, including Kate, opt for a dress or skirt, which should fall just above the knee or longer, with no minis allowed. Trouser suits are allowed but must be of a matching colour or material.
When it comes to tops, spaghetti straps are banned and shoulder straps are required to be at least one inch wide - although jackets and pashminas can be worn over the top.
This also means strapless, off the shoulder and halter necks are not permitted - as are sheer fabrics or visible midriffs.
A newer garment that has been added to the code in recent years is jumpsuits, with Duchess Sophie donning one a few years ago. However, these must fall below the knee and comply with shoulder strap rules.
Meanwhile, when it comes to Royal Ascot fashion, the race meeting is best known for its colourful and intricate hats. Hats must be worn in the Royal Enclosure with fascinators banned. In fact, a headpiece must have a minimum base diameter of four inches.
Male dress code
When it comes to male guests in the Royal Enclosure, the rules are just as strict, with morning suits and top hats to be worn pretty much at all times.
Suits have to be black, grey or navy in colour and also include a waistcoat and neck ties as well as a black or grey top hat - with customised headpieces banned.
Hats must be worn at all times, unless in a restaurant, private box, a terrace, balcony or garden.
When it comes to the feet, only black smart shoes will do, and socks must cover the ankle.
The only way men don't have to wear a morning suit in the Royal Enclosure is if they are an overseas visitor - and then they are eligible to wear military uniform or national dress.
However, the rules state that if national dress does not include a hat - one must be worn.
How to get a Royal Enclosure invitation
To get access to the Royal Enclosure at Royal Ascot, you need to be a member.
You cannot apply for membership as it is invitation-only, unless you are sponsored by two eligible members. A £100 joining fee applies to those who wish to sign up.
Access will give you the chance to see the grass lawns, and sample the posh afternoon tea and expensive dining. Prices of dining in the Royal Enclosure start at an eye-watering £1,499 all the way up to £2,299.
The club used to be specifically for guests of the monarch. Ascot explained: "The origins of the Royal Enclosure can be traced back to 1807 when an area was reserved exclusively for family, guests and the Household of King George III to view the first running of the Gold Cup."
The Gold Cup is the racecourse's most prestigious event and by far the best-known, considered one of the top races in British horse racing.
Access to the enclosure changed later and Ascot said: "The Royal Enclosure as we know it today was established in the mid-nineteenth century when the Emperor of Russia, Nicholas I, visited Ascot for the first time as a guest of Queen Victoria and her husband Prince Albert."
The area in front of the stand became the "most exclusive part of the racecourse" as a result.
