Read our royal correspondent Judy Wade's blog on Kate's fashion choice.
Their thoughts, no doubt, turned to their own big day as they watched the bride and groom walk down the aisle.
Kate Middleton and her fiancé Prince William were both smiling happily as they attended the wedding of their friends Sarah Louise Stourton and Harry Aubrey-Fletcher at the weekend.
Not wanting to deflect attention from the bride, Kate wore a simple black with a sheer neckline teamed with an on trend jacket from Libelula. And completing the look was a pillar box hat, plum cloured heels and a matching clutch.
William – who was an usher - arrived separately at St Andrew's Church in Aldborough, North Yorkshire. He and Prince Harry joined the groom and several friends for an ushers' lunch at a local pub before the service.
After the bride and groom said "I do", a vintage double-decker bus took the guests to a reception at Allerton Park, near Harrowgate.
William and Harry both travelled by Audi A5, however. Before Wills got into his car was heard jokingly telling locals: "It's not my wedding yet."
Other guests at the society wedding included Princess Beatrice and her boyfriend Dave Clarke, and Richard Branson's daughter Holly. Former partners of both Kate and William were also in the congregation.