Other notable guests there to toast Prince Louis were Prince Charles and Camilla, Kate's parents Carole and Michael Middleton, her sister Pippa and her husband James Matthews, and hot bearded Middleton brother James.
The chapel holds tremendous significance for the royal family: Louis' elder brother Prince George was also christened there, and the chapel was where the late Princess Diana's body was laid before her funeral.
Next is Hannah Carter, an old friend of Kate Middleton's from Marlborough College who is married to Robert Carter.
The Duke and Duchess of Cambridge with Prince Louis outside the Lindo Wing at St Mary's Hospital in Paddington, London.
The Lily Font is another piece of royal history present at Louis's christening.
This isn't the first time the young royal's confident personality has come out after she was caught excitedly skipping at a polo event with her mum, Kate Middleton. It will be a busy week, however, for her brother-in-law Prince Harry and new wife Meghan Markle, who were typically affectionate at today's ceremony before their whirlwind trip to Dublin tomorrow.
Van Cutsem's father was one of Prince Charles's closest friends.
Mr. Harry Aubrey-Fletcher attended both Ludgrove prep school and Eton with William.
The duchess, who was wearing Alexander McQueen, added, with a smile: "I hope he stays like this".
The young prince, will be baptised by the Archbishop of Canterbury using water from the River Jordan.
Guests were enjoyed slices of fruit cake from a tier of William and Kate's eight-tier wedding cake at the swanky do.