To me this film felt like a Grand Unified Theory of everything Meryl Streep does brilliantly. Like no other actor living today or before her, you almost never see Streep herself on screen. The last time was when she played herself in a Hollywood restaurant in the Farrelly Brothers' Stuck on You.

Before and since then she's not merely played but been a Polish holocaust survivor, an Italian born housewife in rural middle America or the determined mother superior of a strict 1960s Bronx Catholic school.

She's a pleasure to watch even in her less serious and 'fun' roles like those in It's Complicated, Lemony Snicket's A Series of Unfortunate Events and The River Wild, but The Iron Lady is Streep at the pinnacle of her game. If she announced her retirement from acting tomorrow, there'd never be a creative artist who left on a higher note.

I'll try not to go overboard with the superlatives, but to say she inhabits the body, voice, face and manner of the former British Prime Minister is an understatement. She first appears on screen as the long-retired pollie, in her dotage and possibly sliding into senility as she sees the ghost of the now-dead Dennis (Broadbent, all jolly self depreciation and fun) everywhere.

We see her rise from conservative grocer's daughter to member of parliament, never quite believing she'll make it as far as she does, and before even Margaret herself knows it she rises to the very top through a force of will and determination nobody at the time would credit a woman as having.

The film is mostly complimentary to Thatcher's legacy by virtue of the fact that it's more about the woman than the political climate or her policies. In the final half hour it pays a sort of lip service to her downfall at her own hubris, and it glosses over the worst of her policy failures like the poll tax.

But despite the fact you probably see her rule as one of failure if you're at all left-leaning, there's no denying her determination to do what she thought was right, nor what could be termed flamboyance in an era of stuffiness if only because of her gender.

The somewhat showy 'absolutely non-negotiable' line from the trailer wasn't in the final version I saw, so the actor never outshines the character. When she tells the image advisers priming her for her leadership bid 'that's the message we need to strike', the slightly lazy way the 's' and 't' drawl together will give you shivers if you've ever heard the real Thatcher talk.

That instant right there is what I watch Meryl Streep films for, and she sustains it for as long as she's on screen.