Royal babies are christened in a replica of the intricate lace and satin christening gown made for Queen Victoria’s eldest daughter in 1841.
The Earl and Countess of Wessex’s son Viscount Severn became the first royal baby to wear the new robe at his christening in 2008.
It was made by the Queen's dresser, Angela Kelly, and the team of dressmakers at Buckingham Palace, and features the same lengthy skirt and elaborate collars and bow as its predecessor.
The original Honiton lace and white satin robe, which is now 172 years old, was last used in 2004, after which the Queen commissioned the handmade copy so the historic outfit could be carefully preserved.
The ancient garment was crafted for the christening of Victoria, the Princess Royal, and was used for generation after generation of royal infants including the Queen’s father King George VI, the Queen, the Prince of Wales, the Duke of Cambridge and Prince Harry, with Lady Louise Windsor being the last royal baby to wear the delicate ensemble in 2004.
Traditionally, royal christenings are private affairs, held behind closed doors when the baby is just a few months old and attended only by family, godparents and close friends. A family photograph of the baby in its robe is released to the media.
Royal children are mostly christened by the Archbishop of Canterbury, in the past often in the Music Room at Buckingham Palace where William’s ceremony was held. Prince Harry was christened in St George’s Chapel at Windsor Castle.
The religious ceremony will be a significant occasion for William and Kate’s baby who will, one day, as Sovereign become the Supreme Governor of the Church of England.
Royal babies usually have five or six godparents, although the Prince of Wales had eight.
Contenders for the role for the Cambridges' baby are expected to include the baby's uncles, Prince Harry and James Middleton, and aunt Pippa Middleton, as well as close friends of the couple such as William's old school friend Thomas van Straubenzee or perhaps one of the van Cutsem brothers.
Godparents often also have close historic ties to the royal family. William’s godparents included Lord Romsey, ex-King Constantine of Greece and the Queen’s lady in waiting, Lady Susan Hussey.