David Tennant takes on one of his darkest roles yet in the third series of acclaimed BBC prison drama Time, playing a veteran officer whose carefully ordered life begins to unravel after a major incident inside a young offender institution.

The new series moves the action into a prison for young men, where Tennant’s Bobby Bailey finds himself caught between loyalty to a colleague and the truth about what has happened. As the pressure builds, his story becomes intertwined with that of prison chaplain Marie-Louise, played by Siobhan Finneran, who arrives at the institution struggling with a crisis of faith of her own.

Written by Jimmy McGovern and Samuel Bailey, the three-part drama explores guilt, responsibility and the uneasy moral choices facing both those behind bars and the people tasked with looking after them.

Speaking ahead of the new series, Tennant discussed what makes Bobby such a compelling character, the uncomfortable questions raised by the young offender setting and why he believes some of the programme’s young cast could become major stars.

David Tennant says pressure keeps rising in powerful new series of prison drama

Can you tell us what’s happening in the series when we meet Bobby Bailey?

The series is set in and around a young offender institution where my character, Bobby, is an officer. We follow what’s happening to him both at the prison and in his home life. We also follow what’s happening to some of the inmates and find out about why they’re there and what’s going on in their lives. Something happens towards the end of the first episode and Bobby’s left in a position where he knows more than the authorities do. He has to reckon with himself as to whether it’s right to be honest and truthful or defend his mate.

Bobby is a complex character – can you tell us a bit more about him?

Bobby is written very obliquely and sparely in some ways. You build up who he is by lots of micro experiences of him. He’s very different at work to how he is at home. He’s holding secrets at work. He’s someone who, in some ways, has atrophied. His life was in a routine that he wasn’t particularly interested in challenging, but he has been forced to challenge it by circumstances, both domestic and professional.

He’s forced into moments of crisis that he did not go looking for and doesn’t particularly thrive in, yet he is forced to move. I think that’s what Jimmy has always been famous for, he puts ordinary people in moments of extremis and sort of lets them be, lets them unfold. That’s what his work has always been for me, it’s the human experience kind of twisted and tested. That’s why a prison environment is such fertile ground for him because it’s people in a very unique, very difficult, very extreme situations. It’s like he gets humanity and puts it on a slow simmer and sees what happens. That’s certainly what’s happening to Bobby throughout this, the heat is just gradually being turned up and there’s nothing he can do to turn it back down again. From an acting point of view, that’s what’s appealing and exciting. That’s what draws you to a project like this. You’re telling a story that feels very relatable and rather panic inducing!

Do you think that Bobby is a good person?

I think he’s a very human person. He’s very explicable and easy to identify with. Sometimes he’s a very good man and sometimes he’s quite flawed. I think he has some very good intentions, but he’s also quite compromised. It’s very difficult to answer whether he’s good or bad – he’s both, like all of us.

Time tells the human story of the people in these institutions, do you think things are elevated in a young offender institution?

Each series of Time has been very much its own thing – apart from Siobhan’s character, there isn’t really a link between the series other than it’s about life in prison – a male prison, a female prison, and now a young offender institution. They’re both similar and very different. The prison system is a necessary part of the justice system, but it’s often regarded as imperfect, and yet those working within it often have the best intentions. Clearly when you’re dealing with young men, boys, who are being excluded from society, being locked away, it’s particularly difficult to consider. They’ve done some very serious things and they’re paying the price for that, but I think it’s always important that, as a society, we look at what we’re doing – whether we’re doing the right thing and what it does to the boys we lock away.

Why is setting this story inside a young offender institution a compelling choice?

There’s something about it being boys who are not yet men, who are all potential, and that potential being incarcerated. There’s something very galling about that. It’s quite scary because there’s a lot of energy in that moment in a young man’s life, in a boy’s life. It’s all that potential and it’s bottled and contained, which doesn’t feel right somehow. There’s a real sense of danger in that.

The young actors are brilliant – can you talk about the dynamic working with them?

I think one of the most exciting things about this is some of the young actors that Amy Hubbard, our casting director, and Paul Whittington, our director, have found. It was a big old search and they found some actors who have quite a lot of experience, some lads who are absolutely brand new to it, others who are looking to go to drama school – all different stages of an acting career, yet they’ve come in with such enthusiasm and energy. They’re all so committed and full of life. Working in and amongst them has been quite humbling for me. It’s very moving to see what they’re all bringing to it, they’re all very individual. I think this is one of those series people will look back on in 20, 30 years – I’ll be long gone, I’ll be dust - but you’ll be going: ‘oh my god, that’s where he started! And him, and him, and him!’ I feel very proud to be standing alongside them. That will be the beating heart of the show, their performances.

How has it been working with Siobhan?

I’ve been a fan of Siobhan for years. We’d never worked together, our paths may have vaguely crossed at a do or something, but to get to work with her and to get to know her… She’s everything you hope she will be – as an actor, she’s sublime, and as a human, she’s hilarious. Siobhan Finneran, doesn’t disappoint. You can have that, Siobhan, you can put that on your CV!