Save Me star Phil Dunster on the real leaders of stage and screen

British actor Phil Dunster might be a rising star on our TV screens, but in the world of theatre he has long been making waves with his complex and conflicted characters. Nominated for a 2016 Olivier Award for his role in Pink Mist – a play inspired by young Bristolian veterans about the aftershocks of modern warfare – Dunster then went on to wow audiences in the West End in The Entertainer as part of Sir Kenneth Branagh's theatre company.

On screen, he's enjoyed roles in last year's Murder on the Orient Express and the upcoming series of hit show Humans, and now he's about to hit our screens in Lennie James' Save Me. The star of The Walking Dead stars as Nelson Rowe, an estranged parent accused of abducting his 16-year-old daughter Jody, with Suranne Jones co-starring as Jody's mother Claire.

Dunster plays Jody's ambivalent step-brother BJ McGory, who is privy to his father Barry's secrets and fiercely loyal. Now, as he steps into another thrilling role, Dunster speaks exclusively to Tempus about being wowed by James' script, working with Branagh, and what it really takes to lead a company of actors…

What attracted you to Save Me?
The first time I read the script I was struck by the way that Lennie James has written it, it was such a fast-paced, energetic, visceral script. Knowing he was going to have a huge part in it as well as write it, well I'm a huge fan so that was a massive draw for me. Later, the director Nick Murphy sent us an incredible note asking us to approach the shoot in a very specific way. So right from the get go I knew this would be something really special.

It sounds like Nick Murphy had a huge impact. What was in that note?
He said, 'I want you to crumple the script.' He wanted as few degrees of separation possible between what the character was feeling or wanted, and what the viewer then sees on screen. Nick had a real methodology in how we could make the parts feel natural, and really trusted us as actors to do what needed to do to get there, which meant a lot and made it a really special experience. One of the joys of filming Save Me was to feel so trusted by the people at the helm. >>

Related: Oscar-winning costume designer Alexandra Byrne on 'feisty' Daisy Ridley and dressing up a Murder on the Orient Express

What was the atmosphere like on set?
Suranne [Jones] was amazing to be on set with. For someone who's such an incredible actor, she still manages to be so kind and generous both on screen and off. She's so lovely to everyone throughout the cast and crew and was a great person to have on set, especially in the world of our 'family' within the show. I spent a lot of time with Barry Ward, who plays my dad. We played a lot of chess during downtime, and the cast all played a bit of football as well in the garden of where we were shooting.

You are an accomplished stage actor as well. Is there a difference in how you approach TV?
I don't know if there's much difference. I learn my lines as best I can, try not to be too difficult and that's it. I don't have any rituals. If I have a lot of scenes with someone I like to spend as much time with them as I can and really get a feel of what they think. My training is in theatre, and so to be on stage as part of a company does feel a lot more natural to me. What I love most is the rehearsal time before you open a play. It's a sacred, joyous period before you put the show, where you can't really get stuff wrong. You feel supported and it's a lovely safe place to be – I think when it works you can see that the company is having fun on stage.

You were nominated for an Olivier Award for Pink Mist. That must be an incredible highlight of your career so far.
Pink Mist was an amazing company to be part of, and for me it's definitely a highlight, particularly because we were doing it in Bristol which is where I trained and a city that I love. One of the most amazing things about Pink Mist was speaking to veterans who had been affected by PTSD. It was a very humbling experience, and we all felt that it was very important for us to tell the story in the right way. I'm also lucky enough to have worked with Ken Branagh's theatre company in The Entertainer – that was huge for me. It was such a treat to go to work every day.

You then went on to land a role in Branagh's Murder on the Orient Express. Would you say he's a real influence to you?
He's the daddy! He's a real leader of a company. Ken's extremely loyal to his theatre company and crew, and he brought a lot of people from The Entertainer onto Orient Express. He's absolutely inspiring. One of things you see with Ken is that there's always so much going on (he was running the theatre company and playing the lead in The Entertainer while prepping to direct and star in Murder on the Orient Express. Yet with all that going on he just had laser focus while in our rehearsals, and then went on to deliver every performance. He clearly has an approach and a process that means he can take it all on and do it spectacularly well – and he's got incredible powers of delegation. >>

Related: How BAFTA is paying tribute to the Ridley Scott effect

Do you have plans to focus more on screen? What do you look for in a role?
I'd like to do it all, theatre, television, film. I'm not sure yet where my focus should be, but I love having a role that you can lose yourself in. Those parts tend to find you sometimes – roles that have real conflict, that are dramatic to play. I think conflict is the heart of any brilliant character.

What do you hope viewers will take away from Save Me
I think the pace of Save Me is so thrilling – it's a thriller at its heart – but I hope the viewers will see that the stakes are constantly being ramped up, and the margins for error become smaller and smaller. I really hope viewers will feel like they know these characters by the end, so it's even more powerful because the stakes are so high. It's an episode-turner!

All episodes of Save Me are available from 28 February on Sky Atlantic and NOW TV