Royal christenings are steeped in tradition, with customs passed down through the generations.
When Prince Louis is baptised on Monday at the Chapel Royal, the Duke and Duchess of Cambridge are expected to keep to convention.
Louis is expected to wear the royal christening robe – a replica of the original Honiton lace and satin robe made in 1841 for Queen Victoria’s eldest daughter.
The new robe was created by the Queen’s dresser Angela Kelly.
The original cream lace and white satin robe was last used in 2004 and is too delicate to be worn.
According to tradition, the water used for Louis’s christening will be holy water from the River Jordan, where it is said Jesus was baptised by John the Baptist.
Louis will also be expected to be christened using the ornate silver gilt Lily Font – part of the Crown Jewels.
It is decorated with lilies and ivy foliage around the rim, features three cherubs around the base, and the main bowl is a large lily bloom.
The Chapel Royal at St James’s Palace, London, was used for Prince George’s christening in 2013.
Royal christenings are usually private affairs and most royal babies have been christened at royal palaces.
William and the Prince of Wales were both christened in Buckingham Palace’s Music Room.
The Queen, then Princess Elizabeth, was christened in the Palace’s private chapel in 1926.
Prince Harry, now the Duke of Sussex, was christened in St George’s Chapel, Windsor Castle, where he was married in May.
Princess Charlotte, however, was christened at the Church of St Mary Magdalene at Sandringham in Norfolk.
She was pushed to her christening past well-wishers in a vintage 1950s silver-wheeled Millson pram – once used for the Queen’s youngest children Prince Andrew and Prince Edward.