The Constant Gardener has taken the top prizes at the British Independent Film Awards (BIFA), being named best film.
The Constant Gardener is a political thriller set in Africa
Ralph Fiennes and Rachel Weisz, who star in the John Le Carre thriller, were named best actor and actress.
Neil Marshall's smaller budget film The Descent took awards for best director and technical achievement.
The BIFAs honour films produced and co-produced by UK companies. Downfall, following Adolf Hitler's final days, was best foreign independent film.
The Constant Gardener is the story of a British diplomat (Fiennes) whose wife threatens to expose the pharmaceutical companies testing drugs on innocent Africans.
The awards' winners were chosen by a 13-strong jury which included actors Alan Cumming and Ashley Walters.
The most promising newcomer award went to Emily Barclay for her role in the UK and New Zealand film In My Father's Den, with Matthew MacFadyen.
Best documentary was Sean McAllister's The Liberace of Baghdad, which followed Iraqi pianist Samir Peter as he waited for his US visa while sheltering in a Baghdad hotel.
The eighth annual BIFAs were hosted in west London by actor James Nesbitt, with presenters including Hugh Dancy, Vanessa Redgrave and director Ken Loach.
Rosamund Pike took the supporting actress award for her role as Elizabeth Malet in The Libertine.
Downfall follows Adolf Hitler's final days in his Berlin bunker
Pride and Prejudice actress Keira Knightley received the Variety UK personality award, while Narnia star Tilda Swinton took the Richard Harris award, given annually to recognise outstanding achievement.
Best screenplay award was given to Frank Cottrell Boyce for Millions and the special jury prize was awarded to veteran producer Sandy Lieberson.
The Constant Gardener's success was a further triumph for UK producer Simon Channing Williams, who also worked on Vera Drake which dominated last year's BIFAs with six awards.
British Independent Film Awards 2005:
Best British independent film:
The Constant Gardener
Ralph Fiennes - The Constant Gardener
Rachel Weisz - The Constant Gardener
Best supporting actor/actress:
Rosamund Pike - The Libertine
Most promising newcomer:
Emily Barclay - In My Father's Den
Neil Marshall - The Descent
Frank Cottrell Boyce - Millions
Douglas Hickox Award (for debut director):
Annie Griffin - Festival
Best technical achievement:
Jon Harris - The Descent
Best achievement in production:
Best foreign film:
The Liberace of Baghdad
The Raindance Award:
Variety UK Personality of the Year:
Special Jury Prize:
Richard Harris Award for Outstanding Achievement:
Best British short film: