Wedding rehearsal for Kate and her Prince at friend's society nuptials

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.

Rose Farquhar – who arrived wearing an oversized fur hat – dated the second-in-line to the throne soon after he left Eton, in the summer of 2000. Meanwhile Willem Marx was Kate's boyfriend when she attended Marlborough College in Wiltshire.

The groom, Harry - one of William's oldest friends – has known him since his Eton days. He is the youngest son of Sir Henry Aubrey-Fletcher, 8th Baronet and Lord Lieutenant of Buckinghamshire.

And the bride Sarah Louise is the eldest daughter of the multi-titled Edward Stourton, the 24th Baron Stourton, 28th Baron Segrave and 27th Baron Mowbray.

After the Saturday night reception, William and Kate stayed overnight before heading home to celebrate her 29th birthday on Sunday.

The elegant brunette had a low key celebration with family. A royal spokesperson said she would be spending her birthday "privately".