The strict dress code for each of the Royal Ascot's four enclosures

Whether attending the Royal or Windsor Enclosure, make sure to get the dress code right

Spectators arrive at Royal Ascot in 1913. Getty Images

A women at Royal Ascot circa 1920 wears a white charmeuse and georgette Grecian dress, a wide-brimmed hat decorated with feathers and short gloves. Getty Images

Visitors to Ascot racecourse in June 1921, dressed in their finery. Getty Images

Alice Pearl, Lady Montagu of Beaulieu at Ascot races in June, 1927. Getty Images

Visitors to the second day of the races at Ascot in June, 1927. Getty Images

Women arrive at the race on June 12, 1951. Getty Images

Racehorse owner Madame Suzy Volterra at Royal Ascot on June 17, 1952. Getty Images

Model Fiona Campbell-Walter, as known as Baroness Thyssen-Bornemisza, wears a black straw hat and a white corded suit in 1953. Getty Images

June Laverick attends the first day of the Ascot races on June 18, 1957. Getty Images

Journalist and novelist Una-Mary Parker arrived wearing a flamboyant hat decorated with red silk rose. Getty Images

Queen Elizabeth II and Prince Philip arrive in a carriage in June, 1969. Getty Images

US actor Larry Hagman raising his hat at the Royal Ascot races June 10, 1980. Getty Images

Australian comedian Barry Humphries, dressed as his most famous character Dame Edna Everage, in a hat based on the Sydney Opera House. Getty Images

British actress Nina Baden-Semper attends the races at Ascot in 1972. Getty Images

US actress Rita Hayworth arriving at Ascot on June 13, 1950. Getty Images

A woman wearing a white organza hat during Royal Ascot on June 22, 1972. Getty Images

Models Marie Helvin and Jerry Hall at Royal Ascot in 1982. Getty Images

Sheikh Mohammed Bin Rashid, Vice President and Ruler of Dubai, at Royal Ascot in 1987. Photo: Allsport

Ascot visitors' outfits in 1982. Photo: Allsport

A women wears a pink hat in 1995. Photo: Allsport

Trinny Woodall arrives at Ascot for Ladies Day in June, 2001. Photo: Allsport

Alice Ascoli attends Ladies Day in a hat made of three hats in 2004. Getty Images

Princess Eugenie and Prince Michael of Kent attend Ladies Day on June 18, 2009. Getty Images

Danielle Lineker attends Royal Ascot on June 15, 2010. Getty Images

A women dresses as Marie Antoinette, 2011. Getty Images

The Royal Ascot is back, with the famous horse racing event taking place between Tuesday and Saturday. Held at the Ascot Racecourse in Berkshire, UK, the five-day event brings together many of the top horses of Ireland and the UK, to compete across 28 races, for a total prize fund of more than Dh38.6million.

This year, the event is back to full capacity, with one of the most anticipated fashion events — Ladies Day — happening on Thursday. It's where women turn out in the biggest, most extravagant hats imaginable.

To view the race, spectator spaces are divided into four enclosures, each with its own dress code. To help race goers navigate them, Ascot now has its own website and style guide that lists the do's and don't of what to wear, highlighting the importance of getting it right.

Scroll through the gallery above to see Royal Ascot looks through the years.

Arriving in the wrong outfit will not run the risk of being barred from an enclosure that you have spent a lot to get into, but could have you being asked to leave the event completely. Here, we break it down by area. There are four enclosures, of which only three are open to the public, as the Royal Enclosure is reserved for members and their guests.

Royal Enclosure

As the grandest of the four enclosures, there is little surprise it has the strictest rules for what visitors can and cannot wear.

Ladies must wear formal daywear to access the Royal Enclosure, which can be a dress or top and skirt, but must fall to below the knee, or longer. Best practice is also to cover the shoulders and upper arms — however, a strappy top or dress is permissible if the straps are wider than 2.5 centimetres. Strapless, spaghetti, halterneck, off-the-shoulder or Bardot necklines are not acceptable.

Straps or sleeves must not be sheer or see-through, however, lace is permitted. While trouser suits are welcome, the trousers must be full length, and both elements of matching material and colour. As an alternative, jumpsuits are acceptable, but like hemlines, must fall below the knee. Shorts or anything that expose the midriff are an absolute no-no.

Women are required to wear a hat at all times at Ascot, and within the Royal Enclosure, this can also mean a headpiece but only if the solid base has a diameter greater than 10cm. A fascinator is not allowed.

Men are expected to dress up too, and a black, grey or navy morning dress, complete with a waistcoat, is required for this area. Men must wear a tie — not a cravat or bow tie — and only wear black shoes with socks. Top hats are also required, but unlike for women, men are permitted to remove headwear if at a restaurant, in a private box, at a private club or at the terrace, balcony or garden.

They are not permitted to customise top hats with ribbons, bands or badges, and must not wear a novelty waistcoat. Discreet patterns and anything of a "patriotic" nature is allowed as long as the colours are subdued. So if you have been yearning to wear that Union Jack waistcoat that has been stashed for years, you are in luck, as long as it is not too bright.

In every enclosure, those wearing national dress or in military service dress are welcome.

Queen Anne Enclosure

As this is still formal, guests are reminded to dress accordingly, however, it is a little more relaxed than the Royal Enclosure. For women, this means the head must still be covered at all times, but now a hat, a headpiece and a fascinator are all deemed fitting.

Like the Royal Enclosure, women's outfits must not be strapless, off the shoulder, Bardot or one-shouldered, but a backless dress is acceptable, as long as it is not strapless or any other of the above restrictions. Trousers suits and jumpsuits are both fine but have to follow the same guidelines as the Royal Enclosure, and culottes are also admissible, but only if they fall below the knee. Shorts still are not, regardless of length.

Men are required to wear a full-length suit in matching pattern and colour, with a collared shirt and tie. Again, bow ties and cravats are not permitted, and while shoes no longer have to be black, they should adhere to dark colours. Socks also need to be worn and must cover the ankle. Jeans, trainers or chino trousers are off limits.

Village Enclosure

While the written dress code remains the same as for the first two enclosures, in reality, is it far more laid-back. Women must still wear a hat, but this can be extended to a styled turban, a halo of feathers or a fascinator.

Separates are now a safe option, but keep things complementary, such as a patterned pink blouse over a plain pink skirt to retain a "polished" air.

As this enclosure is on grass, the venue suggests wearing block heels or wedges instead of stilettos to avoid sinking into the mud, and to keep hat sizes small, preferably a fascinator as not to block the view.

Men, meanwhile, must wear full-length trousers and a jacket, although these do not have to match, and as before, must wear a collared shirt and a tie. Ties can be colourful, but again, discreet patterning/decoration is encouraged.

Windsor Enclosure

This has the most relaxed code of all, with suggestions to wear "smart attire" topped with a hat or fascinator. For women, this can mean printed silk pyjamas with a fascinator, or a tea dress with low heels, and a feathered Alice band.

Men can also relax, and while encouraged to wear a jacket, collared shirt and full-length trousers, these do not have to match, so enjoy artfully mixing check trousers with a blazer, as long as it comes with a tie.