The actress insists there's no "direct correlation" between her ancestor William McGovern and Harrison Ford's movie character - but she can understand why many would find her grandfather's story fascinating.
"He was reputedly the first white man ever to enter Lhasa. He entered by staining his skin a darker colour and pretending not to be a white man.
"He wrote a book called To Lhasa in Disguise. He was a very fascinating man I didn't know very well.
"He had children and became a professor at Northwestern in Evanston near Chicago, so he had by that time settled down in his life. It is an amazing story."
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