Michelle Williams plays screen goddess Marilyn Monroe to Kenneth Branagh's Sir Laurence Olivier in this dramatised account of the turbulent production of their 1956 comedy The Prince and the Showgirl. The on-set drama is seen through the eyes - and adapted from the memoirs - of Colin Clark (Eddie Redmayne), a young production assistant who found himself playing consort and confidante to the troubled bombshell. With the Oscar-nominated Williams standing out amidst the cream-of-the-crop cast (which includes 21st century mini-icon Emma Watson), My Week With Marilyn is a work of pure class.
A who's who of luvvies. A dash of Fifties glamour. A whiff of Hollywood scandal. Call the BBC costume department and break out the custard creams; I feel another mostly very British triumph coming on.
Glorious though Cranford director Simon Curtis's production looks, however, all pales in comparison to Michelle Williams' embodiment of Marilyn Monroe. Gee but she's good.
Based on fact (if you believe Colin Clark's reminiscences), this is the story of what happened when the biggest movie star in the world came to London to make The Prince And The Showgirl with the biggest theatre star in the world.
It's no secret that when dear old classically trained pro Sir Laurence Olivier met the erratic bundle of insecurities that was Marilyn, there was much ado about pretty much everything.
Sweeping on to the set late - always late - with her limpet-like acting coach Paula Strasberg (Zoe Wanamaker), Marilyn drives poor Larry to distraction with her ill-prepared, pill-popping, Method-acting madness.
"They wouldn't put up with this at the Hippodrome in Eastbourne!" he wails.
Given her recent marriage to playwright Arthur Miller (Dougray Scott), there's even more concern when she takes a shine to young production hand Colin (Redmayne), a self-proclaimed 'nobody'.
Naturally, Colin is all too keen to be at her beckon call, upsetting her entourage - Strasberg, agent Arthur Jacobs (Toby Jones), business partner Milton Greene (Dominic Cooper) - and forgetting about the pretty wardrobe girl he's been schmoozing (Watson) to join Marilyn at her Berkshire retreat.
With Colin, she can forget playing the movie star and be herself. But while they share a bed and go skinny-dipping, there was, it appears, no serious boop-boop-be-doop.
Of course, it couldn't last. Indeed, sceptics have wondered just how many of Clark's recollections, published in 1995, happened at all.
Veracity notwithstanding, Curtis's snappy direction ensures that events unfold apace. And as we've come to expect from the Beeb, the production values are splendid.
So too the theatricals, with Judi Dench warmly sympathetic as Marilyn's co-star Dame Sybil Thorndike and, despite limited screen time, Julia Ormond the picture of dignity and resignation as Olivier's wife, the waning star Vivien Leigh.
In the main roles, Redmayne engages with old Etonian charm and though Branagh's portrayal of Olivier occasionally tends towards a comedy-sketch party piece, it's never less than entertaining.
But Michelle Williams - wow.
While reprising Marilyn's on-screen antics with aplomb, she skilfully treads the line between impersonation and interpretation to nail the essence of the icon: the breathy delivery, the wiggle, the giggle, the media darling, the little girl lost.
It's a performance of astonishing authenticity. It's just... wow.