William was announced as the patron of the air ambulance's anniversary campaign, enabling him to "champion those working on the frontline, and highlight the importance of the London Air Ambulance's rapid response to incidents, and cutting-edge medical care", his office said. Almost 20-years after the paparazzi-induced death of William's late mother, the prince released a statement via Clarence House encouraging the press to leave his girlfriend alone.
Prince William visited London's Air Ambulance Charity at the The Royal London Hospital.
Kate received other birthday wishes from around the globe, with royal households, British embassies and charities which she supports as patron posting their congratulations.
2011: Newly engaged (and planning the wedding of a lifetime), Kate and William kept her 29th low-key, celebrating at home after returning from friends Sarah Louise Stourton and Harry Aubrey-Fletcher's wedding in Yorkshire.
There was an extra present, a model helicopter, for George and his father quipped: "I can not go back without a helicopter, George will never forgive me".
William will reportedly join his wife and family during the evening to mark Middleton's big day.
William also served almost five years as a helicopter pilot with the RAF's Search and Rescue Force. The first one was a plush helicopter, ideal for William and Kate's newborn.
After his engagement, he will no doubt be heading off to celebrate with his wife and kids.
Previous year the heavily pregnant Duchess spent the day with her family at Kensington Palace.