Duchess of Cambridge opts for low-key 30th birthday celebration She and the Duke of Cambridge will spend the weekend visiting close friends and family, including the Duchess's parents in Berkshire, before heading to London for their first official engagement of the year. The couple will attend the premiere of the Steven Spielberg film War Horse tomorrow at the Odeon cinema in Leicester Square, where the Duchess is likely to be handed early birthday cards and gifts by well-wishers. But that will be the closest she will come to a public celebration of her landmark birthday. "There won't be a big, glitzy party to celebrate the Duchess's birthday," said a royal insider. Monday will just be a very ordinary day for her and the Duke. They will mark the occasion with a low-key celebration with family and friends, but that will be it. There are no plans for a big bash later in the year. They're just not the sort of people who would go big-time on a 30th birthday. The Duchess, who is six months older than her husband, opted for a similarly low-profile celebration for her hen night before the Royal wedding last April. On that occasion she invited a few close friends round for a private party more than a month before the wedding. Former university friends have said in the past that even as a student, the then Miss Middleton was only an occasional drinker, and was never seen drunk.