The Duchess of Sussex was also with the Queen at the event.
Meghan Markle wore a pink Prada dress at the Buckingham Palace reception.
She was criticised by some for crossing her legs in an official photograph with the Queen taken on the day.
But what did a body language expert have to say about Meghan’s performance at the palace?
Judi James, a body language expert, questioned whether we are in danger of losing the “free-wheeling feminist Meghan to the kind of royal protocol body language ‘rules’ that even the top royal women seem utterly oblivious of when they appear in public.”
She claimed that the Duchess of Sussex is trying her utmost to impress the royals.
Judi said: “The effort displayed in her non-verbal signals here suggest she’s trying terribly hard to gain approval from the crown.”
However, she suggests the royal rules may be less stringent than Meghan expects.
Judi said: “A closer inspection of the Queen’s body language might teach her that symmetric, confident and even comfortable-looking sitting positions are equally appropriate for a royal, and that a bag that hangs over the arm can be placed on the ground to avoid balancing and fiddling with the dreaded clutch purse.”
Meghan wore a Prada clutch bag to the event, a style note many suggested the Duchess of Sussex had adopted from Kate Middleton.
However, Judi suggested the bag style is best left to the mother-of-three.
She said: “Only Kate can carry this pesky style of clutch bag without looking too hampered and even she tends to hold the thing in front of her torso with both hands like a mini-barrier at times.
“For a woman like Meghan who is used to her hands-free satchel bags and who made her solo walk up the aisle at her own wedding a tension and anxiety-free zone this pinning down of her own expressive, tactile and more spontaneous side means the royal family could be in danger of losing one of their greatest assets in terms of creating connection with modern women.”
A later image of Meghan casting the clutch aside demonstrates the expert’s point.
She said: “This is authentic Meghan in full flight: animated about her subject and hugely eloquent.
“I love the way the pesky clutch bag has been shoved unceremoniously under her arm and clamped there as she speaks, allowing her to adopt a much more businesslike pose.
“With her head tilted forward and her teeth slightly clenched she is clearly into her message here and those splayed fingers on her raised hands add emphasis that illustrates her interest and passion for her subject-matter.”
Meghan Markle at Prince Louis’ christening wore a pretty olive green ensemble.
She appeared to be wearing the now sold-out Manolo Blahnik BB Suede Pointed-Toe Pump in Olive.
Similar shoes in different colours cost around $584.95 (£442.24) from the designer’s website.