However the Queen, 92, and Prince Philip, 97, were notable absences as it was confirmed that they were unable to attend the christening service due to their busy royal schedules.
It was a family affair for the Middletons, who all stepped out on Monday afternoon to celebrate Prince Louis' christening.
Hannah Carter: Formerly Hannah Gillingham, she went to school with Kate at Marlborough College. From the outside looking in the trio have always appears to share similar fashion sensibilities, with the youngest Middleton daughter particularly taking notes from straight out of her Duchess sister's book. Kate looked radiant as she pushed the vintage Millson pram that her grandmother-in-law the Queen used in the 1950s for her sons Prince Andrew and Prince Edward. Picture: AAPNicholas van Cutsem is another godparent.
The Cambridges have previously chosen close friends and confidantes for the role.
Gazza's message for Southgate and his England squad
England failed to get out of the group at the previous World Cup and two years ago they were embarrassingly dumped out of Euro 2016 by Iceland.
The duchess added, with a smile: "I hope he stays like this".
Prince Charles and Camilla also came out for the christening.
Welby, who will baptise the baby by pouring holy water from the River Jordan over his head, said the event would be "very nerve-wracking" but "a great privilege".
Press Association The Duke and Duchess of Sussex depart after attending Prince Louis' christening. That gown was worn for all Royal Christenings, including The Queen, her children, and seven of her eight grandchildren.
Guests were served slices of christening cake, which is a tier taken from The Duke and Duchess of Cambridge's wedding cake.