Three Billboards outside Ebbing, Missouri picked up the coveted best film award as it claimed five gongs at the 71st BAFTA Awards.
It also won the outstanding British film and best original screenplay awards, with Frances McDormand scooping best actress and Sam Rockwell winning best supporting actor.
Picking up the best film award, British director Martin McDonagh said he was "overwhelmed".
"This is a film that is a hopeful one in lots of ways, but it is also an angry one," he said.
"And as we have seen, sometimes anger is the only way to get people to listen and change, so we're thrilled that BAFTA has recognised this."
In a nod to Time's Up, a campaign supporting victims of sexual assault and harassment, McDonagh said: "This is about a woman who refuses to take any s*** any more, played by a woman who also refuses to take any s***."
Gary Oldman won the best actor award for his portrayal of Sir Winston Churchill in Darkest Hour, which also took the award for best makeup and hair.
Accepting his award, Oldman thanked the former prime minister, who he said "held the line for honour, for integrity and freedom, for his nation".
"I thank you Sir Winston, I thank you and the Churchill family and, of course once again, BAFTA, I'm so grateful for this incredible honour."
British actor Daniel Kaluuya won the EE Rising Star award, following a year in which he received plaudits for his lead role in horror film Get Out.
He said: "I am a product of arts funding within the United Kingdom, and I'd like to thank the people that financially support that."
Kaluuya also thanked his mother, who was sitting in the audience, and said: "Mum, you're the reason why I started, the reason why I'm here, and the reason why I keep going. Thank you for everything - this is yours."
Allison Janney won best supporting actress for her role in I, Tonya, and danced her way to the stage to collect her award.
Meanwhile, Call Me By Your Name screenwriter James Ivory picked up the award for adapted screenplay.
He said the gong "means a lot to me" as it marked the first time he had picked up a BAFTA by himself, and for writing a film.
The BAFTA for best director went to Guillermo del Toro for The Shape Of Water.
Starring Sally Hawkins as a mute cleaner, the film also won best original music and best production design.
In her first ceremony after taking over from long-running host Stephen Fry, Joanna Lumley paid tribute to the "powerful Time's Up movement, and with it, the determination to eradicate the abuse of women all over the world".
Among those who attended the star-studded event were the Duke and Duchess of Cambridge, with Kate showing off her baby bump in a dark green floor-length gown.
At the end of the ceremony, Prince William presented Sir Ridley Scott with the Fellowship award, given by BAFTA to someone who has made an exceptional contribution to film.
"The recipient of this year's Fellowship - the highest honour the Academy can bestow - is a true cinema great," William said.
"His films are amongst my own personal favourites.
"A director and producer whose work has engaged audiences for 40 years, and whose creativity continues to inspire the vital next generation of talent...please welcome to the stage, Sir Ridley Scott."
The full list of winners:
Best film - Three Billboards Outside Ebbing, Missouri
Leading actress - Frances McDormand, Three Billboards Outside Ebbing, Missouri
Leading actor - Gary Oldman, Darkest Hour
Supporting actress - Allison Janney, I, Tonya
Supporting actor - Sam Rockwell, Three Billboards Outside Ebbing, Missouri
Director - Guillermo del Toro, The Shape of Water
EE Rising Star award - Daniel Kaluuya
Outstanding British film - Three Billboards Outside Ebbing, Missouri
Original screenplay - Three Billboards Outside Ebbing, Missouri - Martin McDonagh
Adapted screenplay - Call Me By Your Name, James Ivory
Fellowship - Sir Ridley Scott
Cinematography - Blade Runner 2049, Roger Deakins
Editing - Baby Driver, Jonathan Amos, Paul Machliss
Production design - The Shape Of Water, Paul Austerberry, Jeff Melvin, Shane Vieau
Documentary - I Am Not Your Negro, Raoul Peck
Animated film - Coco, Lee Unkrich, Darla K Anderson
Original music - The Shape Of Water, Alexandre Desplat
Sound - Dunkirk, Alex Gibson, Richard King, Gregg Landaker, Gary A Rizzo, Mark Weingarten
Costume design - Phantom Thread, Mark Bridges
Make-up and hair - Darkest Hour, David Malinowski, Ivana Primorac, Lucy Sibbick, Kazuhiro Tsuji
Special visual effects - Blade Runner 2049, Richard R Hoover, Paul Lambert, Gerd Nefzer, John Nelson