And, she will be hosting President Donald Trump this Friday at Windsor Castle.
Louis, who is fifth in line to the throne, will be baptised today by the Archbishop of Canterbury Justin Welby, in the Chapel Royal at St James's Palace at 4pm today.
The 36-year-old stood to The Queen's left hand side and slightly behind her, as senior members of the royal family watched an historic fly-past on Tuesday afternoon to celebrate 100 years of the RAF. Picture: AAPGuy Pelly has been announced as one of six godparents of Prince Louis.
The Lily Font, which was commission by Queen Victoria and Prince Albert in 1840 and used for every christening since, and water from the River Jordan were used during the baptism.
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The Times-Herald Record reports the celebrity couple were in Nature's Pantry in New Windsor, N.Y., on Wednesday. She completed the look with grey sweatpants, white sneakers, oversized sunglass and a huge smile.
The Duke and Duchess of Sussex had some sweet interactions with youngsters, with one little boy, 3-year-old Walter Cullen, reaching for Meghan's hair and even her face.
It wasn't too long ago that Meghan arrived at a family wedding in a loose-fitting Oscar de la Renta dress, leading to speculation the couple may already be expecting. The former Suits star previously elaborated on her relationship with him. The duchess wore a Ralph Lauren dress, a Stephen Jones hat, Manolo Blahnik shoes, as well as gloves and a clutch.
The duchess, who was wearing Alexander McQueen, added, with a smile: "I hope he stays like this". But it was largely hidden behind Prince Louis' christening gown. She complemented the look with a low bun and a pair of black pumps.
They also served part of the cake at Prince George and Princess Charlotte's christenings.