The huge international success of Scandi noir dramas such as The Killing and The Bridge has given television makers the confidence to bring a new crossover series to the world’s screens – a bilingual Welsh-English crime drama.

Set in and around the steel-town landscape of Port Talbot in south Wales, Bang is being hailed as the first major bilingual series to be aired by the Welsh language broadcaster S4C.

But the drama’s creators – who describe it as the the story of a brother, a sister and a gun – hope it will find an audience across the UK, as it can be viewed on the BBC iPlayer with subtitles. In addition, Bang has already been sold to Sweden and there is hope many other countries will buy the rights.

The makers believe the series, beginning on Sunday night, will win Welsh- and English-speaking fans but are also braced for criticism from those who feel that S4C should solely be in Welsh.

Roger Williams, Bang’s creator, writer and executive producer, said he did not set out to write a bilingual drama but the project grew organically.

“It was very much about story,” he said. “It was about telling a strong story that would get people tuning in every week to see what would happen.”

Williams said he got the idea to set the story in Port Talbot while walking the wonderful beach there and gazing across to both the striking industrial landscape and the hills and mountains beyond. There is Hollywood heritage here: both Richard Burton and Anthony Hopkins were born in the area and Michael Sheen grew up in Port Talbot. “I could not believe that nobody had rooted a drama series in the area before,” said Williams. “It looks so beautiful on the screen.

“Then the conversation about language started to happen. Port Talbot isn’t the strongest place for the Welsh language. There are quite a small percentage of speakers compared with Carmarthenshire, Ceredigion, Gwynedd.

Facebook Twitter Pinterest Catrin Stewart plays Gina, an ambitious cop, in the new S4C drama based in Port Talbot. Photograph: S4C

“From that stumbling block I started to think: ‘Why don’t we reflect the linguistic diversity of a place like Port Talbot?’ For all of us who are bilingual, the reality is that we live our lives through two languages. At home I speak Welsh with my son. At work I speak Welsh, but if I go into a shop or cafe in, say Neath, I’m going to have to use English. That’s my reality.”

He based the central characters, brother and sister Sam (Jacob Ifan) and Gina (Catrin Stewart) on a family of Welsh speakers who live in a “sea of English language” on the Sandfields estate in Port Talbot. They are bound both by a traumatic childhood experience and their Welsh language.

Williams, a Bafta-winning former chairman of the Writers’ Guild of Great Britain, said there was no formula to how language was used. “It was a case of deciding which were our English-speaking characters, and then allowing the story to dictate how much of each language is in each show. The idea is that the dialogue switches between English and Welsh – as happens in real life.

“In the first episode there is a hell of a lot of English. There are other episodes focusing more on the brother and sister and their intimacy, where there’s less English. It felt very creative to have a palette of languages to play with.”

When each new episode first goes out, Welsh speakers can watch it without subtitles. Thereafter on the Friday night repeat and on the iPlayer and SC4 website non-Welsh speakers will be helped by subtitles.

Williams said he hoped the series would bring more non-Welsh speakers to S4C and increase the profile of Welsh drama – and Wales – across the world.

Facebook Twitter Pinterest Port Talbot in south Wales: Bang’s creator, Roger Williams, decided to base the series there while walking on the nearby beach. Photograph: S4C

“I’ve been bracing myself for the criticism. I’m certain there are some people out there who feel that we shouldn’t have a single word of English in the show, but we feel we are doing something that was quite new, quite exciting.”

Ifan said the filming felt natural. “I believe that the way we have filmed Bang is actually reflective of how people do exist and speak in Wales. I’ll be speaking one language to one person and then we’ll switch.”

Champions of Welsh language and commentators will certainly be watching with interest.

Lee Waters, a member of the Welsh assembly’s culture, Welsh language and communications committee, said: “In many communities, Welsh is an everyday language, and people slip easily between English and Welsh. But the unwitting side-effect of creating a Welsh language television channel has been to take Welsh off the screens of the majority.

“I think the popularity of Nordic dramas has given commissioners the confidence that viewers are quite comfortable with other languages. I’d like bilingual programmes to become the norm.

“If we want more people to speak Welsh it’s essential we portray it as an everyday language and an important part of that is television capturing the use of Welsh in everyday life.”