The Ascot Racecourse was founded in 1711 by Queen Anne. The Royal Ascot is the centrepiece of Ascot's year and dates back to 1911. That's when the week of races in the third week of June became a Royal Week.
Every year the Royal Ascot is attended by Elizabeth II and other members of the British Royal Family. They arrive each day in a horse-drawn carriage with a Royal procession to start things off followed by the raising of the Royal Standard and the playing of the National Anthem.
Royal Ascot is a major event in the British social calendar, and press coverage of the attendees and their attire often exceeds coverage of the actual racing.
Some 300,000 racegoers are expected to descend on the Berkshire racing meet over the next five days.
Each day of the week begins with the Royal Procession, when the Queen and accompanying members of the Royal Family arrive along the track in horse-drawn landaus. Today HM was joined by The Duke of York (her son Andrew) and The King and Queen of the Netherlands.
The Prince of Wales, The Duchess of Cornwall and The Duke and Duchess of Cambridge followed.
The Princess Royal, The Earl and The Countess of Wessex, Princess Eugenie and Princess Beatrice were next in the procession!
Princess Kate wore a cornflower blue dress with sheer sleeves by Elie Saab and a matching Philip Treacy hat with a flower detail. People are raving about how great she looks!
Writing in the opening day's official race programme, the Queen said:
"Racing began at Ascot over 300 years ago and while much has changed, the horses remain the stars, thrilling us with their beauty, brilliance and courage. The quality and depth of competition at the royal meeting has also continued to prosper, with eight group one races taking place this week.
The best horses and jockeys from across the globe are increasingly drawn to Royal Ascot, and it is truly exciting to welcome competitors from overseas, as strong international competition adds further interest and fascination."
As the rain fell William and Kate also gave an award to the winning jockey James Doyle who chatted to the royals for a few minutes before they left for the royal box.