The star's acclaimed movie about the real-life 1979 Iranian hostage crisis beat out the likes of Les Miserables, Life Of Pi, Lincoln and Zero Dark Thirty for the ceremony's main prize.
He was also named Best Director, ahead of fierce competitors Michael Haneke (Amour), Quentin Tarantino (Django Unchained), Ang Lee (Life Of Pi), and Kathryn Bigelow (Zero Dark Thirty).
In the acting categories, Daniel Day-Lewis continued to rule over awards season by picking up the Best Actor trophy for his turn as U.S. President Abraham Lincoln in Lincoln, with the Best Actress title going to French screen legend Emmanuelle Riva for Amour.
Anne Hathaway (Les Miserables) and Christoph Waltz (Django Unchained) triumphed in the Best Supporting Actress/Actor categories respectively.
The event was held at London's Royal Opera House and was hosted by British comedian Stephen Fry.