Selena Gomez presents an Oscar-winning film at the London Film Festival

US singer and actress Selena Gomez joined her co-stars on the red carpet at the London Film Festival on Friday for the UK premiere of her Oscar-winning film Emilia Pérez.

The Spanish-language musical was one of the biggest hits at the Cannes Film Festival earlier this year, where Gomez and three of her co-stars were jointly named best actress.

The others – Zoe Saldaña, Adriana Paz, Karla Sofía Gascón – appeared alongside Gomez in London, where the film hopes to continue its momentum in the awards race.

Emilia Pérez follows a Mexican cartel leader (played by Gascón) who asks a powerful lawyer named Rita (Saldaña) to help him fake his own death.

But the reason why he wants to retire and disappear from the world of crime is not what you would expect – the cartel leader wants to change gender and live a new life as a woman.

The rest of the film focuses on four women, including the newly transformed Emilia Pérez, each pursuing their own version of happiness in modern Mexico.

Pérez is portrayed by Spanish trans actress Gascón, who is considered a possible contender for best actress in the upcoming awards race.

Gomez plays the drug lord's wife who remains in the dark about her former lover's new identity, while Paz plays Emilia's new post-transition romantic interest.

All four stars of the film walked the red carpet ahead of the film's UK premiere at the Royal Festival Hall on Friday as part of the London Film Festival.

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French director Jacques Audiard came up with the idea for the film after reading a chapter in Boris Razon's 2018 novel “Écoute,” about a drug lord who changes his identity.

Audiard took the film one step further and made it a story about gender transition.

“I was less interested in changing her identity to escape rival drug lords and more interested in changing her identity for the good of who she was and is,” the director told BBC News. “I was more interested in the past and what led to this transition.”

The role required a very specific person – a trans actress who spoke Spanish and could also sing and dance.

Recalling the casting process, Gascón tells BBC News: “When I was in Mexico, I was contacted by a production team and told: 'We need an actress as crazy as you – you're the only one playing this role.' can, but you have to learn five songs for tomorrow!'

“And I thought, 'OK, let's record the whole album and we'll go on tour as soon as you want!'” she joked. “But I said, 'This is going to be difficult, it's not me.'” But the team on the film worked incredibly well with me, really helped me with all the songs and made sure we could do the best job possible.”

When asked about Gascón's casting, Audiard simply added: “Without her there would be no film.”

Interestingly, the actress committed to playing both the male and female roles – in other words, the character both before and after the transition.

Audiard had originally intended to have another actor play the male drug lord Manitas because, as the director explained, he was “unweary of asking (Gascón) to reconsider something that she was moving away from.”

But Gascón recalled: “I said to Jacques, 'I want to play this role throughout the entire story arc, because for me it's important to play the role fully.' It wouldn't be the same film if another actor (Manitas) played.

That meant using effects and makeup like a fake beard, she explained, in order to be able to play the drug lord in the first part of the musical.

“This movie is this movie because the same actress played the entire performance,” Gascón continued. “You only get a role like this once in your life and I didn’t want to miss the opportunity to play it.”

Reviews for “Emilia Pérez,” which hits Netflix next month, have been overwhelmingly positive so far.

“It’s a wild, dark, glitter-soaked ride that defies convention and classification.” said Maureen Lee Lenker of Entertainment Weekly.

She praised the film's performance, commenting, “Selena Gomez is a welcome surprise, shedding any remaining hints of her Disney Channel origins in her portrayal of a hard-nosed drug agent's wife.”

“The film's climax, in particular, allows Gomez to shine in new ways as a dramatic actress. She conveys heartbreak and fear through a tortured physicality that catapults her into the unpredictable state of a woman on the verge of something dangerous.”

Asked by Graham Norton of the BBC If it was comfortable returning to the world of singing and dancing for the musical, Gomez said, “No, because this was completely different.”

“They were complicated dance moves that I never knew my body could do, and I was also playing a character, so if anything I tried to avoid what I was comfortable with.”

There was also praise for Gascón, a “wonderful discovery” who delivers “a great performance”. according to David Rooney of The Hollywood Reporter.

The Telegraph's Tim Robey described the film as “astonishingly self-aware – it's smart, serious, ridiculous, knowing, powerful and absolutely crazy”, while Inverse's Hoai-Tran Bui said it was “an emotionally fulfilling triumph”.

However, not all critics were so enthusiastic about the film.

“Emilia Pérez was originally intended as an opera, which perhaps partly explains its sweet sentimentality, repetitive lyrics and divergent storylines. But that doesn’t excuse the almost random, whiplash-inducing tone changes.” said Kyle Turner of Slant.

However, Lauren Bradshaw from Fangirl Freakout said: “Emilia Pérez is a sublime, genre-bending thrill-seeker that goes beyond the typical film construct and brings a new sense of excitement to the way we think about film.”

As an actress, Gomez is best known for her starring role in Only Murders in the Building, but also has a successful singing career with hits such as “Back To You,” “Wolves” and “Love You Like a Love Song.”

Her co-star Saldaña has appeared in numerous blockbusters over the past two decades, including the films “Avatar” and “Guardians of the Galaxy.”

It remains to be seen whether Emilia Pérez could be a major award winner, but Academy voters may see an opportunity to recognize Saldaña's box office success in this critically acclaimed work.

Her co-star Adriana Paz is a Mexican actress who has appeared in “Not Forgotten,” “Hilda,” and “La Caridad,” among others.

But the film's breakout star is arguably Gascón, who already had a successful acting career before his move in 2018.

Rooney praised her performance in his review, saying: “The warmth, the joyful self-realization, the complexity and authenticity… that (Gascón's) characterization illuminates undoubtedly have much to do with the parallels in the Spanish star's life – in her own words.” She was an actress before she was an actress and a father before she was a mother.

Emilia Pérez has already been selected as the French entry for the Best International Feature Film category at the Oscars, which will take place in March.