Meryl Streep took to a specially-laid blue carpet for the European premiere of The Iron Lady, the biopic of former British Prime Minister Margaret Thatcher which could win her an Oscar.

She was someone with a big ambition and who made an enormous mark on her time

Ms Streep braved the drizzle to walk up the carpet – matching Thatcher’s trademark blue outfits and her Conservative party’s traditional colour – at the BFI Southbank in central London on Wednesday.

Her performance as the grocer’s daughter who changed the face of Britain has earned her a Golden Globe nomination, putting her in line to win the third Oscar of her career next month.

While Ms Streep’s acting has won acclaim, Thursday’s early reviews were mixed.

Times reviewer Kate Muir gave the film three stars out of five, calling it a “performance of great depth that is condemned to stay in the shallow end”.

Ms Muir criticised the film’s “emphasis on feminism over politics” which left the Thatcher years “almost unrecognisable”.

The staunchly-Conservative Daily Mail awarded only two stars, running the headline: “An Oscar prospect, yes..but a great film? No! No! No!”, echoing one of Thatcher’s most famous speeches.

Ms Streep downplayed the talk of another Academy Award, focusing instead on the challenge of playing the former British premier from the start of her political career to an old age troubled by dementia.

“She was someone with a big ambition and who made an enormous mark on her time. She was arguably the strongest and the only female leader in the Western world at her time, so she broke ground,” Ms Streep told reporters as she arrived for the premiere.

“But beyond that, it was an opportunity to play someone at the waning of her life... and that interested me too because there aren’t very many films that pay attention to older ladies.”

The film has already opened in Australia and the US, but its premiere at a venue along the Thames from the Houses of Parliament, which Baroness Thatcher dominated from 1979 to 1990, has special resonance. Few of Baroness Thatcher’s Cabinet colleagues or rivals have seen the film, which only opened in Britain yesterday, yet many who have say Ms Streep has captured the essence of the woman whose legacy is still the subject of intense debate.

Film critics have pointed to Ms Streep’s bouffant hair and clothes in the role as near-perfect, and the distinctive voice which Baroness Thatcher worked so hard to perfect booms throughout the film.

Ms Streep confessed she knew little about Baroness Thatcher’s policies before accepting the role but defended the decision to make a film about a woman who remains a divisive figure in Britain.

“That was part of what made it interesting, because people tended to look at her either as the saviour or the destroyer of the UK. And at this point in time the feelings are still as vehement it seems to me,” she said atthe premiere.

Director Phyllida Lloyd – the woman behind the Abba smash hit Mamma Mia! – starts the action in the present day, with an elderly Thatcher clearing out her late husband Denis’s clothes.

The ghost of Denis, played by Jim Broadbent, himself an Oscar winner in 2002, is ever present as his wife looks back on her career as she rises from modest beginnings to become Britain’s first and still only woman premier.

Baroness Thatcher took over a country whose economy was sorely in need of modernisation, yet the often ruthless way she achieved her goals continues to divide opinion, as does the war over the Falklands.

Yet Ms Streep also shows Baroness Thatcher’s undoubted toughness as she brushes off the IRA’s attempt to kill her in the bombing of a Brighton hotel in 1984. Some critics say it brushes over key issues such as her bitter dispute with the coal miners, which gripped Britain in the mid-1980s, and some have argued it is insensitive to portray her in such a way, while she is still alive.

Ms Lloyd revealed on Wednesday that Baroness Thatcher’s family had turned down an invitation to a public screening of the film.

“We did make contact with the family some time ago to tell them what we were trying to do but they perhaps quite understandably have sort of stepped back from the whole thing.

“I can quite understand them not wanting to see it in the public gaze so we are not actually sure whether they have seen it or not.”