Much of the talk before Sunday’s Oscars ceremony was about Hollywood’s moral compass.

After 2016’s Oscars So White debacle and the Time’s Up movement, attention was particularly drawn towards how the awards show would approach diversity and, in particular, the equitable treatment of areas such as race and sex.

One of the issues that was in rather less sharp focus was disability in Hollywood films. That was until Sunday’s show was stolen by the stars of the Silent Child, a British production about a profoundly deaf child, which won best live-action short film.

The film tells the story of Libby, played by six-year-old Maisie Sly, who struggles to communicate until a social worker, played by Rachel Shenton, teaches her sign language.

Shenton, who also wrote the short, gave her acceptance speech on Sunday in British Sign Language (BSL), fulfilling a promise to Sly, who is profoundly deaf and was in the audience.

Later she said Sly had “held the Oscar, she said it was very heavy, she had her photograph taken with it and then said she wanted to go back and see her brothers and sisters, so she’s keeping it real.”

Prior to the awards ceremony, Sly was pictured on the film’s Twitter account holding a sign that read: “Disability is Diversity,” underlining Shenton’s point that the issue should not be excluded from Hollywood’s introspection.

In her acceptance speech, Shenton said: “This is happening. Millions of children all over the world live in silence and face communication barriers, and particularly access to education.”

Sly was born in Plymouth and when she was two her parents moved the family more than 100 miles to Swindon to gain better access to better specialist education for deaf children for her and her siblings.

She had never acted before but Shenton said Sly had “taken it all in her stride. She always said we’d win.”

Shenton began learning sign-language at the age of 12, after her father went deaf. “Deafness is a silent disability. You can’t see it and it’s not life-threatening, so I want to say the biggest of thank-yous to the academy for allowing us to put this in front of a mainstream audience.”

• This article was amended on 13 June 2018. An earlier version said that Rachel Shenton qualified as a sign-language interpreter at the age of 12. Shenton learnt sign language for herself, however is not a qualified interpreter.