Mahershala Ali has revealed that his part in the upcoming third season of True Detective was originally written as a white character, before Ali stepped in and insisted that he really, really wanted to play it and was willing to ring up half of his family to prove it was a good idea.

"The lead was white, and the other cop was black. And once you see the show, you’ll see that is different from the other seasons, in that the lead character, he’s at the point of the arrowhead," Ali told BlacKkKlansman star John David Washington as part of Variety's chin-stroking chat series Actors On Actors. "I could have played that second lead, the supporting character. But in my mind I was like, 'I’ve done this my entire career. I’ve never done that.'"

To be fair, Ali had just won a Best Actor Oscar; playing second lead might be a little below his paygrade. Keen to prove a point, Ali got on the blower to his cousins for proof that a black cop could really get to the top of the profession in mid-century Arkansas.

"And they send me some pictures of my grandfather in the state police officer uniform. So I texted them to [showrunner Nic Pizzolatto]. And I was like, 'See, we existed in this space in the 60s, in the 70s, [as] state police officers. This is in Arkansas.'"

It did the trick. "I came back to [Pizzolatto] and I was like, 'I want to play that part,'" Ali said. "And he thought about it a couple of days, got back to me, and he was like, 'Yo, let’s do this. I’m down.'"