With so many caricatures of Maggie Thatcher in the ether, from Janet Brown to Spitting Image, it was never going to be easy for any actress to take on the mantle of the redoubtable Iron Lady. Happily Meryl Streep is not just any actress. The 16-time Oscar nominee has delivered a tour de force performance that should see her in the running for a third gong next February.

The Iron Lady opens with an octogenarian Thatcher escaping her minders and shuffling down to her local shop to buy some milk. This is a veiled reference to her early days as Education Secretary when her decision to curtail the provision of free milk to schoolchildren aged between seven and eleven led to outrage and the infamous chant, "Maggie Thatcher, Milk Snatcher".

The present day Thatcher is shown as a woman on the cusp of dementia (she regularly sees and holds conversations with her late husband, Denis). Before long, the movie enters flashback mode and we follow young grocer's daughter Margaret Roberts (excellently played by newcomer Alexandra Roach) as she storms the citadel of a male dominated Conservative Party and quickly progresses through the ranks.

In this regard, there's a striking, worm's-eye image of the huddled masses of MPs entering Parliament in 1959. Rows upon rows of grey slacks and sensible shoes are seen shuffling into the House of Commons punctuated by a single figure in a skirt and high heels as the 34-year-old Member for Finchley first takes her seat in Westminster.

It was always going to be impossible to shoehorn Thatcher's eventful and controversial political life into a two-hour movie so The Iron Lady concentrates on such headline-grabbing events as The Falklands conflict, the Brighton bombing, the miners' strike and the 1981 hunger strikes. Equally importantly on the narrative front, the movie focuses on the woman behind the headlines and how her life changed as she gained the reins of power and, more strikingly, as those reins were eventually whipped away.

Throughout, Meryl Streep delivers an astonishing performance, offering every shade and nuance of one of the most controversial figures of the twentieth century. Elsewhere, Jim Broadbent is terrific in the role of Denis Thatcher; while Olivia Colman makes her mark as Maggie's daughter, Carol. In terms of Thatcher's cabinet, there are some interesting casting choices with Richard E Grant taking on Michael Heseltine and Anthony Head playing Geoffrey Howe. Meanwhile John Sessions pops up as Ted Heath, and Michael Pennington gets to take on the redoubtable Michael Foot.

In truth, the movie itself is a fairly uneven affair that doesn’t quite manage to maintain its dramatic impetus throughout. But this is all about Meryl and it would be a major surprise if her superb performance as the Iron Lady doesn't result in a golden gong (her third) next month. She certainly has my vote. And this man is not for turning.

Michael Doherty