Prince William has served as an usher at the wedding of his friend Hugh Grosvenor, the Duke of Westminster. The event was briefly disrupted by environmental protesters who sprayed orange powder paint from a fire extinguisher as the newlyweds left the church. The 33-year-old Grosvenor is one of Britain's wealthiest landowners. His wedding on Friday to 31-year-old Olivia Henson was one of the high-society events of the year. Onlookers cheered the arrival of Grosvenor, dressed in a morning suit, and Henson, wearing a white wedding dress designed by Emma Victoria Payne. Grosvenor is a godfather to 10-year-old Prince George, the eldest son of William and his wife Catherine. Catherine, who is being treated for cancer, did not attend.