Over the years, the actor, writer and director, 61, notched up a record eight nominations spanning seven categories, but always came away empty-handed – until now.
Belfast, which is set during the Troubles and written and directed by Sir Kenneth, is partly based on his own experiences as a boy and helped him to the prize for best original screenplay on Sunday night.
Speaking in the press room after his win, he said: “I think the thing that stayed with me was just the sense of how much at that time I felt like I knew who I was. I had a very strong sense of who I was.
“Making the film allowed me to return to that. My sister said, ‘This film has really outed you as a kind of working-class Belfast boy’, and, yes, it has.
“This was a way of not just acknowledging but embracing everything about it – the dark and the light.”
Sir Kenneth pays tribute to his birth place in the black and white coming-of-age film starring 11-year-old Jude Hill.
Discussing the child star, he told the PA news agency: “He’s a very special young fella. His parents are here tonight… they’ve done an amazing job with him and the two younger siblings.
“They encourage their kids to be open, funny, ask questions. Jude does all of that.
“The single beef I have with him is that he supports Liverpool Football Club and that meant directing him – as an actor who had to play a role supporting Tottenham Hotspur Football Club – was a challenge, though I did say to him tonight, ‘Listen, if I can do this, then surely Tottenham Hotspur can get fourth place this season and be in Europe next.’
“He disagreed with me.”
Sir Kenneth was born in December 1960 to working-class Protestant parents.
At nine, to escape the Troubles he moved with his family to Reading, where he was bullied for his accent but found comfort in acting.
He graduated from the Royal Academy of Dramatic Art in 1981 and, six weeks later, made his professional stage debut.
In 1984, he joined the prestigious Royal Shakespeare Company (RSC), where he won plaudits for performances in Hamlet and Henry V, earning a reputation as one of the UK’s foremost young talents.
In 1987, he left the RSC to co-found the Renaissance Theatre Company, serving as an actor, writer, and director and helping to further the careers of stars like Dame Judi Dench.
Credited with making Shakespeare accessible to the wider public, Sir Kenneth was later involved in film versions of Much Ado About Nothing, Hamlet and Love’s Labour’s Lost.
He showed further range by branching out into big budget Hollywood productions and, in 2011, directed the Marvel film Thor, starring Chris Hemsworth as the titular Norse god.
In 2018, Sir Kenneth receive the freedom of Belfast.
He directed and starred as Belgian detective Hercule Poirot in 2017 flick Murder on the Orient Express and, more recently, Death on the Nile.
From 1989 to 1995, Sir Kenneth was married to actress Dame Emma Thompson but they split amid media reports of an affair with Helena Bonham Carter.
Since 2003, he has been married to film art director Lindsay Brunnock, who he met while shooting 2002 film Shackleton.