The dress code for Royal Ascot is known to be strict, and the organisers lay out the rules in detail on their website.
Guests in the Royal Enclosure face the most stringent rules, with dress and skirts asked to be “of modest length” falling just above the knee or longer.
Dresses and tops must have straps of one inch or greater, even if covered by a jacket or pashmina.
Hats are required, and they should have a base of four inches – so fascinators are banned.
Rules are more relaxed in the Queen Anne Enclosure and Village Enclosure, and there is no dress code at all in the Windsor Enclosure.
Ladies attending today have pushed the rules to their limit in an attempt to display their unusual style.
One couple dressed in matching tiger print outfits for a bold, shocking look sure to set tongues wagging.
Some ladies ran the fine line between good taste and bad without success, with eye-catching hats causing a stir for all the wrong reasons.
Oversized feathers in complementary colours, gigantic ruffled flowers and even a cut out horse all found their way onto the heads of attendees.
Prints were also popular this year, but without style success for some, as headache-inducing patterns were chosen by several ladies.
As well as a strict dress code, racegoers are facing tight security at the event this year after a spate of recent terror attacks.
Armed police will be patrolling the racecourse, and more extensive dog, bag and physical searches will be carried out this year in the wake of the terror attacks in London and Manchester.
Racegoers were warned that access to the course will take longer and to allow extra time.
Up to 300,000 people are due to descend on the Berkshire event over the next five days, including the Queen who has attended every year since she came to the throne in 1952.
Organisers advised punters via the Ascot website to expect tightened security, saying: “You will notice a stronger armed and uniformed police presence throughout the site and the vicinity.”