The late Queen Elizabeth II broke a 114-year-old rule in 2008 in order for Prince William to be granted a very rare role. The Order of the Garter, with the annual service set to take place in Windsor today, is one of the most recognisable royal traditions.

William previously made history in 2008 after the late Queen made her beloved grandson the 1000th Knight of the Garter. Her decision was also historic for another reason: it meant she broke a rule that had been in place for 114 years.

At the event 18 years ago, William was also the first grandchild to be invested since Queen Victoria did the same for one of her grandsons.

Queen Victoria invested Alfred, Hereditary Prince of Saxe-Coburg and Gotha in 1894.

Still to this day, William remains the only one of the late Queen’s grandsons to be a member – and it remains unclear if this will change.

The Order of the Garter service is an annual parade held in Windsor and was founded by King Edward III in 1348.

Senior members of the Royal Family are set to take part in a procession around the grounds and then travel back to Windsor Castle in horse-drawn carriages.

Prior to this, a private investiture and luncheon is held at the Castle.