But the challenge of bringing Monroe’s complexity to the screen was one thing, becoming a song and dance girl was another, Williams confesses.
“I’m not a singer or a dancer, I haven’t been on stage doing either since I was 10 years old,” Williams tells the Irish Voice.
“Because of that I really felt -- when I was able to put the nerves aside -- a tremendous outpouring of joy.I felt like a little girl whose dreams came true for the first time. And I was able to tap into what I imagine made Marilyn Monroe so luminous in her singing and dancing numbers.
“When you’re in that state your critical mind has to turn off, there’s no room for it. You’re remembering steps and lyrics. That’s what makes those performances of her so magical. She’s not thinking.
“Like everything else in this movie it all took a tremendous amount of preparation. I really started at the very beginning and made my mistakes along the way. And I decided not to be hard on myself about those, but instead realize they were part of the process.”
Clearly Academy Award winning producers David Parfitt and Harvey Weinstein are banking that My Week With Marilyn will turn into another juggernaut like Shakespeare In Love or The King’s Speech – and they’re probably right.
My Week With Marilyn is exactly the kind of Oscar bait the Academy loves -- it’s British, it has Judi Dench, Branagh gives a bravura performance, the costumes and the period detail are well done and it brings you close to Monroe’s personal tragedy without quite tipping over the edge.
If you love Marilyn Monroe you’ll almost certainly enjoy the movie. Williams’s impersonation is particularly good at capturing Monroe’s countless insecurities and her emotional torment, but unfortunately she’s not quite the comic talent that Monroe was.
Marilyn clearly understood she was sexy enough to make fun of her own image without any risk of ever falling flat on her face, but for Williams this is a steeper climb because the truth is she’s just not as skilled a comedienne. That gulf between the two actresses turns out to be an important one and it’s never breached.
Williams is the age now that Marilyn was when she filmed The Prince and the Showgirl. Like Monroe she has known real tragedy (Heath Ledger, her partner in both life and art, was found dead from an apparent drugs overdose in 2008 – an awful parallel with Monroe’s own story).
Like Monroe in person Williams looks flinty and uncomfortable in her own skin, but she also has Monroe’s megawatt charisma and when she smiles it’s a dazzler.
You’ll come away from My Week With Marilyn with a deeper appreciation of both Williams and Monroe’s acting talents, which in the latter case went far beyond filling a curvaceous dress.