The newlyweds posed with the cast of the smash hit musical at a fundraising campaign for Harry's HIV-education charity, Sentebale, when the Duchess of Sussex accidentally dropped the cherished pet name.

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In a clip that is shared with social media, she is asked: "Can you see, my love?"

When others around them reacted, a shameful Meghan, 37, was visibly confused. "Oh!" She giggled, clutching her hand against her chest.

Harry and Meghan share PDA's is hardly rare – they are usually hand in hand or whisper to each other during public outings – but it is the first insight we have had in their private nicknames for each other.

The royal couple looked glamorous as always, with Harry in a navy suit and Meghan in a black Judith and Charles tuxedo jacket. The daring outfit was cut far above her knees and showed her legs.

The prince drew a lot of laughter as he entered the stage at night and offered a few bars You will come back – the song performed by the King George III character, who happens to be the duke's great-grandfather.

"You say …" Harry shrieked, while the theater broke out in laughter and laughter.

"That's enough – he tried, but I said no," he said, gesturing to the creator of the show, Lin-Manuel Miranda, who was behind him. "I do not know how these guys do it, every night and also in this heat."

Miranda later tweeted: "King George III's great-great-great-grandson The Duke of Sussex sang a few bars tonight #Hamilton LDN".