Accepting the prize, which was presented by Cillian Murphy, the Killarney native said that when she was a little girl: “I never in a million years thought I would get to make a film.”
Recalling her early days as an actress, Buckley said: “I had nuclear bad fake tan on, white hoop earrings, a polka-dot red skirt and had the audacity to say one day I wanted to be like Judi Dench.
“This is nuts, this really does belong to the women past, present and future who taught me and continue to teach me how to do it differently.”
Addressing her fellow nominees, the actress said: “You are all just radical and you are doing it for the naughty girls, and I’m in awe of all your incredible performances.”
She added: “I love films and I believe in storytelling. I believe in women’s voices to tell those stories. I share this with my daughter, who has been with me since she was six weeks old on the road with this.
“It’s the best role of my life, being your mum, and I promise to continue to be disobedient so you can belong to a world in all your complete wildness as a young woman. I am very grateful for this.”
Buckley had been hotly tipped for the gong, as she has proved unbeatable through the awards season so far for her performance as Shakespeare’s wife Agnes Hathaway – historically known as Anne – in Hamnet.
The big-screen adaptation of Maggie O’Farrell’s award-winning novel about the family life of William Shakespeare and the death of their young son, directed by Chloe Zhao, broke the record for the most nominations for a female-directed film in Bafta history, with 11.
Hamnet also won the Bafta for Outstanding British Film. Producer Sam Mendes said: “We are not great as an industry or a culture for patting ourselves on the back, but perhaps we should.” He added: “Hamnet was an act of faith, a quiet epic about love and loss and grief.”
One Battle After Another was named Best Film, with director Paul Thomas Anderson saying it was a “tremendous honour”, adding: “Anybody who says that movies aren’t good any more can piss right off because this is a great f**king year. We have a line from Nina Simone we used in our film, ‘I know what freedom is, it’s no fear’. Let’s keep making things without fear, it’s a good idea.”
He also landed the Best Director award for One Battle After Another.
Robert Aramayo won the Best Actor Bafta for I Swear, in which he portrayed Scottish Tourette syndrome campaigner John Davidson. He also won the EE Rising Star Bafta.
Irish actors Cillian Murphy and Paul Mescal were also in attendance. Mescal was nominated for his portrayal of Shakespeare in Hamnet, while Steve – in which Murphy played a headteacher at a reform school in the 1990s – was nominated for Outstanding British Film.