Tristan Gemmill spills the details of his week-long courtroom drama The Case (BBC1, daytime, from Monday)…

What do we need to know about The Case?

“It’s a hard-hitting daytime courtroom thriller and legal drama, which focuses on one case over the course of five episodes, showing this week from Monday to Friday.”

What’s the case in question?

“It’s a murder! Wonderful Dean Andrews plays Tony Powell, a garage mechanic accused of killing his lover Saskia. His defence is that he agreed to help Saskia, who was terminally ill and bedridden at home with bone cancer, in an assisted suicide.”

And it’s not a simple legal proceeding?

“It’s got a lot of elements. Mum of two Saskia divorced her policeman husband Neil (Connor McIntyre) for a second chance of love with Tony. During the trial proceedings it transpires she changed her will in favour of Tony before she died. Tony claims Neil is prejudiced against him and that he also took the videotape Saskia made explaining her decision.”

You play defending barrister Sol Ridley – what sort of man is he?

“This is Sol’s first time being entirely in charge of a murder case and he’s excited by the prospect. However his weakness is he occasionally allows his emotions to rule his head. Over the five episodes you see him fighting that battle in his head.”

Does he believe Tony’s innocent?

“There is the question of whether or not a lawyer’s state of mind towards a client’s innocence or guilt affects how they defend the person. Sol has to deal with Tony’s reticence about the events and his inability to communicate what he’s thinking. There are lots of twists and turns along the way that will take viewers by surprise.”

And does this affect his ability to defend Tony?

“Sol’s opponent in court is prosecutor Mark Metzler (Sean Chapman) who knows Sol sometimes lets his emotions go to his head. Mark spends an awful lot of time picking apart Tony’s testimony and also making little digs towards Sol trying to get a rise out of him! Meanwhile, Sol’s also got a growing attraction for his pupil barrister Julie…”

So there’s some romance!

“There is! We never meet Sol’s wife, but it’s established he’s in an unhappy marriage. It raises a few eyebrows when he takes Julie on as his assistant some people think it’s the classic case of an older barrister taking advantage of the young trainee.”

Did you enjoy getting out of Casualty scrubs and into a wig and gown?

The wigs and gowns are really quite warm, I can tell you! But it does make you feel the part. After playing a doctor for four years it was good to get my head in a different space.”

Have you stayed in touch with the Casualty cast and crew?

“Yes, I saw them all recently. They’ve done the big move to Cardiff and they asked me to go down, so I’m going to have a look. I’m very excited about it!”