Sigourney Weaver Wows on the Red Carpet at BFI Film Festival in London

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Sigourney Weaver may play a grandmother in her latest movie, but she certainly doesn't look it.

The 66-year-old actress stunned at the premiere of A Monster Calls at the BFI Film Festival in London on Thursday.

WATCH: Sigourney Weaver, Neill Blomkamp Tease 'Alien' Follow-up

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Weaver looked comfortable yet chic as she walked the red carpet in a tan blouse, black trousers and a matching coat.

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In between posing for photographers, the actress also kindly met with fans to sign autographs -- and a photo of herself as Ellen Ripley from Alien!

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It's hard to believe it's been 37 years since the first of the Alien films was released, but the cast has clearly still go it.

In fact, Weaver recently reunited with old co-stars Bill Paxton, Lance Henriksen, Michael Biehn, Paul Reiser and Carrie Henn at this year's Comic-Con, where they dished on giving the sci-fi series another go.

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"There is an incredible script," Weaver confirmed of the next installment, written by Neill Blomkamp.

"He has work to do. I have work to do," she teased, optimistically. "But I'm hoping when we finish those jobs, we'll circle around and do it."

See more in the video below.