The world's greatest bike race got off to a flying start today, as the Duke and Duchess of Cambridge welcomed the Tour de France to Britain with a spectacular display by the Red Arrows.
The Duke and Duchess were joined by Prince Harry to welcome the world's best cyclists for the "Grand Depart" of the 101st Tour de France.
Deputy Prime Minister Nick Clegg was also there.
Crowds of fans cheered loudly as the cyclists gathered outside the 18th century stately home Harewood House, where they took off their helmets as they were greeted with a rendition of the French and British national anthems, performed by the Band of the Corps of Royal Engineers.
British reigning Tour de France champion Chris Froome looked relaxed as he talked to the royal party, while Mark Cavendish, who is hoping to win today's sprint finish, beamed and appeared to thank Kate for coming.
The duchess then cut the ribbon to officially start the race.
The RAF's Red Arrows delighted crowds by performing a flyover that left a trail of red, white and blue vapour - the national colours of France and the UK.
The Duke and Duchess and Prince Harry watched from just next to the start line as the teams sped down the hill and out of the park, and William was heard to say: "The only better view would have been on the back of one of those motorbikes."
Spectators flocked from all over the country to cheer on Froome as he hopes to retain the winner's famous yellow jersey he won last year, while excited locals will be hoping fellow Briton Cavendish will pedal to victory in the first stage in his mother's home town of Harrogate.
The 198 racers enjoyed clear skies and bright sunshine as they left Leeds town hall at 11am in a leisurely ceremonial start, and began racing in earnest when they departed Harewood House.
Riders will pedal 190.5km from Leeds to Harrogate, weaving through the Yorkshire Dales and Moors and taking in three ferocious climbs.
After the Tour's launch, the Duke and Duchess of Cambridge and Prince Harry visited the small North Yorkshire village of West Tanfield.
Thousands of people, who had lined the streets since early this morning, cheered as the royal party arrived.
The village, near Ripon, has even commissioned its own beer from the Pennine Brewing Company - the Tour D'Ale - in celebration of the sporting event.
Tomorrow they will arrive in York for a stage taking in some of the most challenging climbs in Britain, ending in Sheffield.
On Monday the Tour moves south to Cambridge with a stage ending beneath the gaze of Buckingham Palace on The Mall in central London - which was also the final finishing line in the 2012 London Olympics cycling road race.
Up to three million people are expected to watch the Tour's two-day visit to Yorkshire.