Prince William fired the gun to start today's Anglesey ultra-marathon.
But it was Duchess Kate who got things going with a bang as she delighted runners and fans with her surprise appearance.
This is the first time that new mom Catherine has been seen at an official public event (she was snapped shopping for groceries earlier this week) since leaving the hospital after Prince George's birth July 22.
Baby Georgie remained at home at their rented farmhouse with his granny as babysitter.
William and Catherine sent runners off for the annual Ring O' Fire Anglesey Coastal Ultra-Marathon, a 135-mile run that circumnavigates the Welsh island. It's part of their long goodbye to the place where they have lived since 2009.
It had to be a little bittersweet for the couple, who will soon leave Anglesey and move back to London with the little prince.
Kate's appearance wasn't a total surprise. Palace officials had hinted she might appear with William at some public event in Wales before leaving for good, and three hours before the marathon started, media officials tweeted she would be there.
The two met volunteers and some of the runners and their families before the start of the event.
Slender as she was before her pregnancy, Kate was dressed in an olive-green tweed short jacket by Ralph Lauren, a dot-patterned Zara top, cropped skinny black jeans and her favorite wedge shoes. He was just as casual in a blue sweater over a blue shirt.
British reporters on the scene reported she told well-wishers she met that the baby prince was doing well, sleeping better at night, that he loves bright-colored objects, and that granny Carole Middleton was staying with them in Wales to help babysit.
Looking relaxed, they joked with each other and with people they met, at one point accepting a gift of diapers. We can always do with more of these, Will laughed.
The Daily Mail reported an insider said that initially she wasn't going to attend the event but "she was also keen for the chance to thank the people of Anglesey herself for the warmth and hospitality they have shown her and the Duke."
Kensington Palace announced this week that Will would officially start the marathon, leading to some initial confusion on Twitter about whether the 31-year-old second-in-line to the throne would be running in the race himself. He is not, even though he may want to.
Set against the dramatic backdrop of the Snowdonia Mountains, the marathon is staged over three days and follows the rugged and spectacular Anglesey Coastal Path around the island, home to the RAF base where Will has worked as a search-and-rescue helicopter pilot since before his marriage to the former Kate Middleton in 2011.
The couple and little George spent their first few weeks after the birth at her parents' estate in Bucklebury outside London, but they have been back in Wales for a couple of weeks. They're finishing up final duties and packing up their rented farmhouse to move into a huge new residence at Kensington Palace by October.
In between, they're likely to spend some time at Balmoral, the royal family's summer holiday estate in Scotland, visiting the baby's great-grandparents, Queen Elizabeth II and Prince Philip.
The couple also are scheduled to appear together in London on Sept. 12 at an awards ceremony staged by the Tusk Trust, a wildlife conservation charity of which Will is patron. A new conservation award has been named in his honor.