She shot to fame in Trainspotting, and has starred in Gosford Park, Boardwalk Empire and even as a Disney princess. So why did the Scottish actor panic about her new role in Line Of Duty?

Kelly Macdonald’s roles are typically quiet, fraught with internal conflict and entailing journeys that are more reflective than active. As a grieving mother in The Child In Time, a gangster’s wife in Boardwalk Empire and the titular role in The Girl In The Cafe, the 45-year-old has, over the last 25 years, become known for the kind of thoughtful performances signified by the image of a woman staring out of a window. All of which makes our encounter today doubly surprising; that Macdonald, appearing via Zoom from her home in Glasgow, is here to talk about Line Of Duty, possibly the least reflective TV show ever made. And that she is a complete hoot.

Her role in Line Of Duty has, over the course of the show’s six seasons, become a coveted one in British telly – that of the guest star brought on as a no-good cop to be investigated by AC-12, the show’s now iconic anti-corruption unit. (Previous incumbents in the just-how-bent-is-she role include Keeley Hawes and Thandie Newton.) Line Of Duty’s twists are legendary, and the embargos fierce, and, following the rollercoaster of season five – in which we grappled, briefly, with the possibility that Supt Hastings (Adrian Dunbar) himself was bent – we meet Macdonald in season six as DCI Jo Davidson, getting stuck into a case. And that is pretty much all, ahead of transmission, the BBC will permit either of us to reveal, which makes Macdonald crack up every time she thinks of it. “It’s hilarious that they sent me a list of things I’m not to talk about, when I can’t remember any of it.”