Meryl Streep has won in the Best Actress category at the Oscars for her portrayal of Margaret Thatcher in The Iron Lady, fending off competition from Michelle Williams, Glenn Close, Viola Davis and Rooney Mara.

Presented the award by Colin Firth, the actor described Streep as "unreasonably good".

"When they called my name, I had this feeling I could hear half of America going, 'Oh no. Come on ... Her, again?' You know. But, whatever," Streep said, rolling her eyes to enthusiastic applause.

She added: "I really want to thank all my colleagues, all my friends. I look out here, and I see my life before my eyes, my old friends, my new friends.

"And really, this is such a great honor. But the thing that counts the most with me is the friendships and love and the sheer joy we have shared making movies together. My friends, thank you, all of you, departed and here, for this inexplicably wonderful career."

The award is Streep's third Oscar of her career.