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 that had been worn for all royal christenings since that of Queen Victoria's eldest daughter in 1841.
Accompanied by her husband, Meghan stunned in a green hat and dress, and according to the team at Meghan's Mirror, wore since-sold out heels by Manolo Blahnik. She also wore her hair in a low chignon, topped with a white, flowered headpiece.
While William was also dressed in full RAF uniform, his ensemble differed slightly to Harry's by wearing a blue sash across his body.
However neither Prince Harry nor Meghan were named among Louis' six godparents, with the honour going to Guy Pelly, who was once dubbed the "court jester", family friend Nicholas van Cutsem and William's school pal Harry Aubrey-Fletcher.
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This was met with a minute-long standing ovation by his supporters, and seated silence from those who still oppose his power grab. Some opposition parliamentarians remained seated while others stood without applauding.
Harry and Meghan will also head to Australia, Fiji, the Kingdom of Tonga and New Zealand in the fall for their first royal tour as a married couple.
Middleton's sister, Pippa Middleton, attended the ceremony, as did her brother James Middleton.
The Queen and Prince Philip were notably absent from the special occasion, however it has been confirmed that the 92-year-old monarch had previously agreed the arrangement with the Duke and Duchess due to work commitments, not health issues.