The British film and television industry is on the brink of a significant “moment of change” that will be driven by women, black people and other minority groups, the actor and comedian Sir Lenny Henry has said.

“How we tell our stories and what sort of stories we tell is changing,” Henry told the Observer at the launch of the BBC’s much-anticipated three-part adaptation of The Long Song, Andrea Levy’s prize-winning novel about life in 19th-century Jamaica during the final days of slavery. “What’s happening is a coalition of all us jumping in and saying: ‘I’ll tell my story, why don’t you tell your story? That’s a good story? Let’s hear that too’.

“It’s a moment of change and it’s going to be driven by women, by black and brown people, people with disabilities, gay people, Jewish people. They’re all pushing to make this multiplicity of stories that will change our lives in the next 20 to 40 years.”

Henry has long campaigned for greater storytelling diversity on our screens, giving evidence to the government’s culture, media and sports committee in 2014, and last month delivering a letter to Downing Street calling for tax reliefs to help boost the number of women, black and minority ethnic and disabled people working in film and TV.

“Tax breaks for representation and inclusion within the industry will open a lot of doors,” he said. “If we can get people to agree to it and to understand that it will benefit the industry, then it will lead to a huge unblocking of people’s minds and allow them to understand the idea of giving everyone a chance. The wider the industry becomes, the greater variety of stories you will see being told. It’s a privileging of several different perspectives so that you don’t just get the same gaze all the time.”

Levy describes the funny, sad, tender and brutal coming-of-age of July (played by Tamara Lawrance) on a plantation “as a personal journey to understand my Caribbean heritage … it’s something that a lot of British people don’t understand that in the British Caribbean, run by the British, slavery went on for 300 years and a society grew up. People lived under it, and they survived it and they died under it, yet it is not as big a part of British history as I would like to see.”

Henry, whose parents came to Britain from Jamaica, agrees. “I didn’t learn about this at school, and when I did find out it was a shock. You begin to think this shit is serious, so why didn’t we learn about it?’ he said. “And I think maybe the answer is that they don’t want to freak out kids of 15 and 16 too much because maybe it is too much to know that an entire country stood by while this was going on for hundreds of years…”

Tamara Lawrance, left, as July and Hayley Atwell as Caroline Mortimer in the TV adaptation of Andrea Levy’s novel The Long Song. Photograph: Carlos Rodriguez/PA

He took the role of watchful plantation butler Godfrey partly because he is a friend of Levy but also because he loved the story. “What’s brilliant about July is she’s cheeky, subversive, anarchic, lovable and yet also a slave,” he says. “It’s really important to be presented with a fully-rounded story that’s not just the horrible stuff, that also shows you the softer side, the subversive side. It would be awful if this was just an ‘eat your veggies’-style drama where you feel you have to watch out of a sense of duty. Andrea’s story and Sarah [Williams]’s scripts contain humour and anarchy and sadness and great, great tragedy and I think those are all the hallmarks of brilliant drama. It means that this is a proper meal.” The historical setting was also particularly important, given the way black actors are often overlooked for period pieces, Henry said. “When you read Peter Fryer’s wonderful Staying Power or David Olusoga’s Black and British, there is evidence that black and brown people have been in the British Isles from way back,” he says. “There was an Ethiopian troop of Roman soldiers at Hadrian’s Wall for God’s sake. Where is their story? There are black Tudors, black Georgians … where are their stories? Or the stories of the Chinese tradesmen walking around Victorian England? It’s the epitome of madness to keep fishing from the same narrow pool and serve only the same narrow demographic.”Instead

Henry hopes that The Long Song’s prominent position in the BBC’s pre-Christmas schedule will lead to more truly diverse programming. “This is a rarity, but it doesn’t have to be,” he said. “We’re all still sitting here on the bench waiting to go on. And we’re ready. We’re ready to write the thing, to perform in the thing, to help to create the thing. And once we are given that chance then you will see more works like The Long Song because there are a million stories to be told in every endeavour of life that can move us and make us laugh and cry and think.”

The Long Song is on BBC One from Tuesday, 18 December, at 9pm for three nights