Film festivals have provided breakthrough moments for actors before now, but for Morfydd Clark to appear in three films, and to play two different roles in one of them, seems excessive.

The Welsh actress has conquered this year’s London Film Festival with triumphant appearances in The Personal History of David Copperfield and Eternal Beauty. And last night her third film, Saint Maud, directed by newcomer Rose Glass, received a prestigious special commendation in the festival’s annual awards.

The judges announced on Saturday night that the overall winner in the best film category was Alejandro Landes’s acclaimed thriller Monos, a gripping portrayal of the lives of child soldiers. Yet they also took time to heap praise on Saint Maud, with the official competition jury president Wash Westmoreland declaring: “This dazzling directorial debut marks the emergence of a powerful new voice in British cinema.”

Clark, who grew up in Cardiff, plays the lead character in the psychological horror film, which tells the story of a troubled carer who becomes disturbingly fixated on the life of her latest charge, an ageing dancer.

The actress, who is perhaps best known for her stage appearance as Cordelia at the Old Vic opposite Glenda Jackson’s acclaimed King Lear, could also be seen at the festival in Eternal Beauty, a comedy drama from Craig Roberts, starring Sally Hawkins. She also amused audiences with her performance as Dora, David Copperfield’s vapid first wife in Armando Iannucci’s adaptation of the novel, chosen as the opening gala premiere. Clark could also be spotted by the keener-eyed critics playing Copperfield’s widowed mother in the same film.

As Dora, Clark had to perform with a lap dog which often threatened to upstage her on the set, the actress has claimed. “We’d occasionally do a scene, and people would be laughing their heads off, and I was like, ‘I must have been really bloody funny’, but Armando would come over, [and say] ‘Sorry, Scampy was hilarious.’ It was the dog!’”

In 2014, Clark appeared in Carol Morley’s boarding school drama The Falling, and she also played the daughter of Kate Beckinsale’s Lady Susan Vernon in Whit Stillman’s 2016 film, Love & Friendship.

Born in Sweden, where her father was working, Clark and her family returned to Wales when she was seven, where she was diagnosed with attention deficit hyperactive disorder (ADHD). Concentrating, she has since explained, is always much easier for her when she is performing.

In this, the 63rd BFI London Film Festival, more than 60% of the films shown in competition were made by a female director or co-director, with producers from 16 countries represented.

Tricia Tuttle, the festival’s director, said on Saturday: “Our awards highlight the most distinctive, urgent and accomplished filmmaking from around the globe, and it has been an incredible festival. Audiences have been moved, provoked and dazzled by these films, many of which engage with pressing social and political themes in very inventive ways.”

Monos, the winning film, has been described as “hallucinogenic and intoxicating”, and has earned comparisons to Apocalypse Now. Festival judges in London hailed it as a masterpiece, while also praising an American film, Alma Har’el’s Honey Boy. Other winners were Mati Diop’s Atlantics, which scooped the Sutherland Award for a first feature, the documentary on the 1970s Rock Against Racism movement,White Riot, which claimed the Grierson Award, and the Iranian short film Gosal (Fault Line).