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/ Source: TODAY
By Ree Hines

Last week marked what would have been the 55th birthday of Princess Diana. The occasion put the iconic royal back in headlines and back in the minds of those who've missed the woman known as the People's Princess.

But now a new documentary is offering another chance to look back at Diana — before she was a princess at all.

In a sneak peek from "Princess Diana: Behind Closed Doors," Mary Robertson remembers the young woman she hired as a nanny telling her about a trip she took to Balmoral castle, the royal family's Scottish getaway.

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Robertson recalled asking the young Diana whether she'd met with Prince Andrew (Prince Charles' younger brother).

"'No, it was actually Charles, but his mother invited me,'" Robertson remembered her saying. "And I just burst out laughing at the thought of her referring to the Queen of England as a friend's mother."

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As for that fateful meeting, Diana didn't think anything special would come from it.

"I did say, 'Oh, my gosh. Do you think anything's going to develop?'" Robertson said. "And very regretfully, you know, staring down at the floor, she said, 'No, I don't think he'd look twice at me. After all, he’s 31 and I’m only 19.'"

"I said, 'I wouldn’t be too sure,'" Robertson said.

RELATED: Princess Diana looks over baby Charlotte in Photoshopped pic that's gone viral

You can see more from "Princess Diana: Behind Closed Doors," which is produced by Peacock Productions, when it airs Saturday at 9 p.m. ET on Reelz.

Follow Ree Hines on Twitter.