Prince Louis was carried into the chapel by his beaming mother, wearing the handmade replica of the Royal Christening Robe, which in 2008 replaced the original which had been worn for all royal christenings since that of Queen Victoria's eldest daughter in 1841.
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".
The Queen and her husband, the Duke of Edinburgh, didn't attend the christening, but it was a decision made "some time ago" and wasn't due to health reasons. Like his siblings Prince George and Princess Charlotte before him, Louis will be dressed up in an article of clothing that carries the weight of history.
Frozen or not, just save us a slice of the royal cake, please.
Proud parents the Duke and Duchess of Cambridge made their way into the service in London with their three children.
The Archbishop of Canterbury welcomed the royals, bending down to greet George and Charlotte, who looked happy and content, at the entrance to the chapel.
Max Mumby/Indigo via Getty Images Prince Louis was born on April 23, 2018 in London, England.
Princess Charlotte has a reputation for being confident in front of the cameras that follow her and her family everywhere.
Hours before the ceremony, Prince Louis' godparents were revealed in an official statement from the palace.
Recently, Meghan Markle was baptised in the chapel ahead of her wedding to Prince Harry, while Kate Middleton was confirmed there before she Wednesday Prince William. At affair, the 34-year-old socialite donned a gorgeous baby blue dress to her nephew's outing that cut a similar style to the Alexander McQueen number her 36-year-old royal sis wore to her 2017 wedding.
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