Film critics have said there is no clear reason why The Constant Gardener failed to pick up more Bafta awards.
The Constant Gardener is based on John Le Carre's novel
Fernando Meirelles' political thriller had been expected to do well at the British Academy film awards on Sunday, after it was nominated in 10 categories.
But The Constant Gardner, about a British diplomat whose wife is murdered when she threatens to expose pharmaceutical companies testing drugs on innocent Africans, won only a single award for editing.
The best film award went to Brokeback Mountain, while best British film was awarded to Nick Park's animated feature Wallace and Gromit: The Curse of the Were Rabbit.
Leading lady and Golden Globe winner Rachel Weisz was left out in the cold when Reese Witherspoon was named best actress, and its star Ralph Fiennes lost out to Philip Seymour Hoffman for Capote.
Leon Forde, deputy features editor at trade magazine Screen International, said there was no obvious answer to why the political thriller did not pick up more Baftas.
"The Constant Gardener is a really well-liked film, was positively received and was seen as a front-runner going into the awards - particularly Rachel Weisz in the best actress category," he said.
"But the competition this year was intense."
He added: "If you look at previous Bafta winners, the academy doesn't automatically give prizes to Brits just because they are British. The organisation judges British films on a level with the best international work and prides itself on that."
The Guardian's film critic Peter Bradshaw said the outcome must have been a "real blow" for everyone involved in the film.
"Brokeback Mountain was a very worthy winner. It is a brilliant film and I don't think anyone can really quarrel with that," he added.
"But I think another reason is the way the Baftas are constructed. They have special awards for best British film and best first British director, as well as best film.
"This causes, what I call, the 'Commonwealth Games' effect. It creates a mentality of we'll give a nice award to a British film, but give the 'Olympic' gold to Hollywood.
"It's only plays a contributory part, but it's an important part."
The Constant Gardener still has one last shot at awards glory, though.
Weisz is nominated for the best supporting actress Oscar, which will be awarded in Los Angeles on 5 March.