The Royal Ascot horse races, one of the biggest events in the social calendar of Britain, began on 18 June with the best of fashion, style and sports. One of the main highlights of this event is hat fashion styles.

The race meetings have seen some superbly stylish and downright funny hat creations.

Many wonder why people attending the Royal Ascot even don hats in the first place, but it is actually a rule set by the organisers of the event, which states that women should dress in a manner that suits the formal occasion.

Among the guidelines for a dress code: headpiece or hat with a base of 4 inches (10 cm) or more in diametre should be worn by ladies at all times.

Royal Ascot is a five-day meeting and one of the highlights of the horse racing calendar. The five-day event is attended by British royals, film stars and international celebrities.     

Bollywood actress and former Miss World Aishwarya Rai Bachchan also attended the event on the very first day as brand ambassador of Longines watches. The 39-year-old actress looked stunningly royal and gorgeous in a black and white lace dress. Following the dress code the actress also donned a charming black and white Philip Treacy hat. 

The event was also attended by Queen Elizabeth, Prince Charles and the Duchess of Cornwall, Princess Eugenie, Prince Andrew, Sophie (Countess of Wessex) and Princesses Beatrice as well as British singer Katherine Jenkins among others.

The Duke and Duchess of Cambridge - Prince William and Kate Middleton - skipped the event ahead of the birth of their child in July.

The Royal Ascot, which is held annually at the famous Berkshire course, has been around for over 300 years. It was first founded by Queen Anne in 1711.

Scroll down to check the photos of unusual hat styles at the Royal Ascot 2013: 

Stylish Hats
Aishwarya Rai Bachchan looks Gorgeous at Royal Ascot
Stylish Hats
British singer Katherine Jenkins attends the first day of the Royal Ascot horse racing festival at Ascot. (Reuters)
Stylish Hats
Britain's Queen Elizabeth, Prince Charles and Camilla Duchess of Cornwall arrive by carriage for the first day of the Royal Ascot horseracing festival at Ascot. (Reuters)
Stylish Hats
Designer Larisa Katz (Reuters)
Stylish Hats
Racegoers at Royal Ascot 2013 (Reuters)
Stylish Hats
Racegoer wear an equine-themed hat
Stylish Hats
Racegoers wear an equine-themed hat
Stylish Hats
Racegoers attend Royal Ascot 2013 (Reuters)