Redmayne plays Colin Clark, an assistant who ends up chaperoning Monroe while she films The Prince and the Showgirl in the UK. Monroe and Olivier's contrasting acting styles lead to tension, and the Hollywood star finds solace in the arms of Clark.
Digital Spy sat down with Redmayne to discuss taking a skinny dip with Williams, British versus American acting styles and how Branagh managed to play Olivier while also directing Marvel blockbuster Thor.
My Week with Marilyn opens in UK cinemas on November 25.
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> Michelle Williams is Marilyn Monroe in My Week with Marilyn trailer