The BAFTA win has bettered Argo's chances at the Oscars on February 24.
Inspired by real-life events in 1979 of CIA's attempt to free six diplomats while posing as a film crew, the film has steadily climbed its way to the top this award season by winning trophies at the Golden Globes, the Producers Guild and the Directors Guild of America awards.
'Argo' beat 'Les Miserables', 'Life Of Pi', 'Lincoln' and 'Zero Dark Thirty' to be named the best film.
Affleck, who was famously snubbed at the Oscars in the best directing nominations, was named best director at the BAFTAs and his film also took the editing trophy. He was pitted against Michael Haneke 'Amour', Quentin Tarantino 'Django Unchained', Ang Lee 'Life Of Pi' and Kathryn Bigelow 'Zero Dark Thirty'.
The actor-director dedicated his directing prize for "anyone out there who's trying to get their second act."
The best picture win by Daniel Day-Lewis for his brilliant turn as 16th US President Abraham Lincoln in 'Lincoln' was predictable. It was the only prize out of 10 nominations for Steven Spielberg directed movie.
Emmanuelle Riva, the 85-year-old French actress, was named best actress for Michael Haneke's old-age drama 'Amour', which also was named best foreign-language film.
'Life of Pi' won trophies in best cinematography and special visual effects categories out of its nine nominations.
Tom Hooper directed musical 'Les Miserables' won four prizes, including an expected best supporting actress trophy for Anne Hathaway.
Hathaway, also a nominee at the Oscars, said she was "overjoyed" to win the best supporting BAFTA.
While accepting the trophy from presenter George Clooney, Hathaway said, "What am I thinking I almost walked past George Clooney without hugging him. That's just stupid." She thanked the cast and fellow co-star Hugh Jackman.
The 23rd James Bond movie 'Skyfall' was named the British film and won in the best music category.
Bigelow's Osama bin Laden hunt thriller was the big loser at the BAFTAs as it came empty handed despite five nominations.
Quentin Tarantino won the original screenplay award for his violent, civil-war slave-revenge drama 'Django Unchained' while actor Christoph Waltz was named best supporting actor for his role of a bounty hunter.
Waltz, who won an Oscar for last Tarantino film 'Inglourious Basterds' and is nominated for a second time in the same category, credited his director for the BAFTA win.
"Why I get to stand here is really no mystery because it says so at the beginning of our movie: 'written and directed by Quentin Tarantino'," he said before thanking other cast and crew members.
"...I need and want to thank you for the thing that touches me the most, your unconditional trust... You silver-penned devil, you."
Tarantino, meanwhile, revealed plans about another film in the series while thanking his actors Waltz and Jamie Foxx for doing "a bang up job with my dialogue."
Writer-director David O Russell won the adapted screenplay prize for 'Silver Linings Playbook', which stars Indian actor Anupam Kher in a key role.
'Brave' won the best animated film while best documentary trophy went to 'Searching for Suger Man'. Best short film trophy went to 'Swimmer', short animation to 'The Making of Longbird'.
Joe Wright's 'Anna Karenina' won in the best costume design. Best Rising star award was given to Juno Temple.
Outstanding debut by a British writer, director or producer went to Bart Layton (director), Dimitri Doganis (producer) for 'The Imposter'
Director Alan Parker received a BAFTA Fellowship, Sunday night's highest honor, for his illustrious career that includes films like 'Midnight Express', 'Fame' and 'Mississippi Burning.'