Also in attendance were Queen Elizabeth II, Prince Charles and his wife, Camila, amongst others.
Meghan wasn't entirely on her own - she was accompanied by Sophie, Countess of Wessex, and Sir Timothy Laurence.
The balconies of the Foreign & Commonwealth Office are small, and only three people at a time are advised to stand on them for events such as this for safety reasons.
Since there is not enough room for all family members to stand on a single balcony, the Queen was joined by the two future Queen Consorts.
That same month, royal expert Katie Nicholl said in an interview with Entertainment Tonight that the pair are "loving parenthood" so much that they might be preparing for bringing in a sibling for Archie.More news: Police in 3 Bolivian cities join opposition
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While the Duchess of Cambridge and Camilla, Duchess of Cornwall, stood beside the monarch, the Duchess of Sussex joined Sophie, Countess of Wessex, on a separate balcony to watch the memorial service in London this morning.
The event is the first time the Sussexes and Cambridges have appeared in public together since Harry and Meghan opened up about their struggles in an emotional television documentary.
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Harry revealed that he and William are on "different paths" and, like all brothers, have their "good days" and "bad days", which resulted in rumours of a rift between them. We will always be brothers. And we were trying to encourage him to have a second baby, " said Susie to Forces Network. Ahead, see more photos of her full outfit.