Kate Middleton Is Radiant, Smiling at Friend's Wedding With Prince William, Prince Harry: Picture

The Duchess of Cambridge, Kate Middleton, and Prince William at the wedding of Mark Tomlinson and Laura Bechtolsheimer in Switzerland, on the 1st March, 2013. Credit: Splash News

It was Olympian Laura Bechtolsheimer's big day, but for a few moments before the bride made her big entrance, all eyes were on another famous Brit: Kate Middleton. The pregnant Duchess was radiant and beaming as she mingled with guests at Bechtolsheimer's wedding to fellow athlete Mark Tomlinson on Saturday, March 2, in Switzerland.

Middleton, 31, arrived at the mountain chapel in the Swiss Alps with her husband's brother, Prince Harry. (Prince William, 30, was already at the venue, fulfilling his duties as an usher.) Keeping her baby bump hidden under a cream coat with brown fur trim -- which she wore with a matching Lock & Co. brown hat, a Max Mara dress, Emmy shoes, an Annoushka pearl necklace, and an Emmy clutch -- the royal mom-to-be waved happily to photographers. At one point, she was seen resting her hand on her growing belly. 

After the ceremony ended at around 2:15 p.m., Bechtolsheimer and her groom left to enjoy a little down time before their reception. As they exited the church, Middleton was seen "throwing white confetti in the air and laughing with joy," an onlooker tells Us Weekly.

The Duchess and her Duke, who has played polo with Tomlinson since they were teens, arrived in Switzerland on March 1. Shortly after settling in, they hit the slopes of the Swiss Alps with Prince Harry. Middleton -- who is due to give birth in July -- was photographed laughing with pals and carrying a sled.

Earlier in the week, the expectant royal did a little maternity shopping at Topshop in London. While there, she picked up a cute floral frock by Lovestruck that retails for just 37 pounds ($55).