During the documentary, viewers will see footage collated over more than a year which ITV boasts will offer "a unique insight into Her Majesty The Queen's role as a figure on the global stage and the baton she is passing to the younger members of the Royal Family".
In a "right time, right moment" situation, the crew caught Meghan's huge smile as she saw her bridal outfit, which included a veil that featured hand-embroider flowers from each of the 53 countries in the Commonwealth.
And he adds: "Have you bumped into the Queen yet?"
"Fifty-three countries, oh my goodness", says the 37-year-old in the clip from the documentary, which will include her first interview since becoming a royal.
A few months ago a fan video surfaced of Meghan introducing herself to onlookers, and the internet went into a spin over her apparent British accent. "It'll keep us busy".
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The facilities were a key test center for its intercontinental ballistic missiles created to reach the United States. The two leaders emerged from a two-day summit in Pyongyang to sign declarations in front of the world's TV cameras.
Speaking with hospitality workers visiting from the Caribbean, in a scheme set up by the monarch, the prince says: "You guys have spent way more time in Buckingham Palace than I ever have - and you've only been here two weeks". Harry asked, before reassuring them: "If you suddenly bump into her in the corridor, don't panic".
The documentary is titled Queen of the World and will air on ITV on Tuesday.
There's no word yet on when Australian or American audiences will get to see the documentary.
The source told "Entertainment Tonight": "She really is taking the new job part of her role seriously having meetings with Palace staff and learning about the Commonwealth so she can support Harry in his new role as Commonwealth Youth Ambassador".