While the Duke of Cambridge played usher at his Etonian friend's big day, it is thought that his wife Kate Middleton stayed at home to look after the royal couple's two-month-old baby Prince George.
The first-time father arrived early to carry out his usher duties at the Norfolk wedding, while Prince Harry and Pippa were later spotted walking into the church with other guests.
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Prince William, who was among 15 other ushers, looked handsome in a dark jacket with tails and grey pinstriped trousers. He completed his immaculate look with a maroon tie and a white rose in his suit pocket.
Prince Harry opted for a brighter outfit, which matched the early afternoon sunshine, and looked just as dapper in a yellow waistcoat and blue tie. Crowds of well-wishers and royal watchers cheered outside the church as they spotted the handsome prince arrive.
Pippa, meanwhile, stole the spotlight in a teal knee-length dress with lace overlay that showed off her tanned and toned legs. The Duchess of Cambridge's younger sister wore a matching hat with peacock feathers, and finished her look with an assortment of gold jewellery.
While it was recently speculated that Pippa had got engaged to her boyfriend Nico Jackson, who did not attend the ceremony, the columnist was not pictured wearing an engagement ring.
Other high-society guests included Prince William's close friends, Guy Pelly and Thomas van Straubenzee, the latter of whom recently got married to Lady Melissa Percy in June.
At Saturday's wedding, guests arrived to the parish church of St Nicholas by tractor trailer, while Lady Laura walked with her father Julian Marsham, the eigth Earl of Romney, from their nearby estate.
The bride looked radiant in a fitted, lace gown that was reminiscent of Kate's iconic wedding dress, which also featured elegant lace sleeves.
William and Kate are close friends of the bride and groom, with James even giving a speech at the royal couple's wedding in 2011.
Hymns could be heard from outside the church during the service, and after the hour-long ceremony the party carried on to the Romney home where the reception was believed to be held.