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. Catherine's sister Pippa, who is expecting her first child, was also in attendance with her husband James Matthews.
On a number of occasions, Prince Harry was seen to be whispering in the 36-year-old's ear and was believed to be talking her through the events across the day and their significance.
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.
The Duke and Duchess of Sussex have also brought along a press team consisting of their own social media press officer, a programme co-ordinator, a PA and an assistant.
For her first trip overseas on official royal duty, Markle looked pretty elegant in a look that resembles something a First Lady would wear.
While Meghan opted for a navy, off-shoulder pleated dress, Kate highlighted her svelte figure in a mint-coloured button-up dress. But it was largely hidden behind Prince Louis' christening gown.
Her hat, by Jane Taylor, was a headband-style piece with floral accents, and completed the elegant look. Think about it: have you ever seen Kate Middleton with a hair out of place?