As Spooks returns to BBC One for a seventh series this autumn, Richard Armitage joins the cast as Lucas North, an MI5 spy who has spent the past eight years languishing in a Russian prison.

What is Lucas like and what’s his background?

“On the surface Lucas is an amiable character but eight years in a Russian prison has had a profound effect on him. His personality is divided between who he was before he was imprisoned, the prisoner and the person he has become. He has an outer façade which is personable, but underneath is somebody who has been through a big trauma. He is aware he is playing catch–up with the world. He was once the best in his field, and now he is trying to regain his former brilliance. He wants to be accepted back onto the Grid – it is the only aspect of his former life that has remained.”

How has he been specifically affected by his eight–year incarceration?

“He is malnourished but physically he’s fit. In prison he put himself through a torturous routine to keep himself going. He was about to break mentally and in order to stop that from happening he kept his body working. He has no knowledge of how damaged he is emotionally, until memories start to work their way to the surface – he experiences flashbacks and begins to remember things buried deep in his subconscious.”

Does Lucas find it difficult to adapt to the outside world?

“There is a scene in one of the early episodes where he is in the safe house and he can’t sleep – the only way he can get to sleep is by lying on the floor, effectively sleeping on a very hard prison bed. There are glimpses that make you realise he is struggling to adjust, but as a spy he keeps it well hidden.”

How do the rest of the team take to him?

“There is obviously suspicion at first. They are inclined to be instantly suspicious of anybody who has been in the hands of the Russians for so long. A situation arises in which he has a chance to prove himself, but Lucas doesn’t play by the rules, in fact, the game he is playing is very dangerous and he pushes the boundaries of trust to the limit. He subsequently has to fight very hard to be accepted and regain Harry’s trust – it’s never fully given and he has to continually prove himself, there is always ambiguity surrounding him.”

How did you find learning to speak Russian and also filming in Russia?

“Learning to speak Russian was pretty impossible, really – I had to learn it phonetically. My biggest problem was that Lucas doesn’t just speak Russian; he passed as a Russian native for years, so I had to really work hard at it. I had to make it seem that it was a second language. It was a challenge but I sat down with a language CD back in November 2007 and I also had a Russian language coach. When we went to shoot in Moscow I found I could communicate and understand some of the things the Russians were saying – that was exciting.

“Shooting in Russia was a great experience – we shot in many different locations. Even though Russia and Moscow have changed beyond recognition in the last decade, the dangerous aspects of it are still there – but perhaps that was in my imagination as I was travelling there as Lucas North. We were filming on the aeroplane so I had to arrive in costume and character! We shot footage during the flight and at the airport and used every second of the day we had there to shoot.”

Was there time for laughing on set?

“Spooks is obviously a serious show, so there is a great need to laugh whenever possible to diffuse the atmosphere. There is often a “gallows” humour between the characters, particularly Harry and Ros, and the writers cleverly manage to get humour into a very serious arena. There was one particularly funny occasion, when I was pulled over by the police and cautioned during a driving sequence. I was asked to open the boot of the vehicle, oblivious as to why. I did as I was told and found most of the camera and sound crew crammed into the boot looking sheepish. We obviously had permission to film and, as all the crew were wearing seat belts, we were ok. The problem was, when asked for my name I told them it was Lucas North and I was working for MI5 – that’s when the director stepped in to save me!”

Spooks is notorious for killing its lead characters. Do you worry this might happen to you?

“To be honest I haven’t thought about it too much. However, on judging the way characters tend to get killed off, I think when Lucas’s time comes I’ll welcome it. When Spooks characters are killed off, or disappear, it’s usually the most memorable moment of the episode, or even series. There are moments in this series that take your breath away – giving that rare feeling of wanting to look away but having to watch compulsively though your fingers.”

How does filming Spooks compare to filming Robin Hood?

“They are both so different. Robin Hood is a fantasy legend and historic piece, so it all feels heightened and dramatic – I arrive on a horse, my character is bombastic and has a particular way of moving and communicating, which is public and aggressive. Lucas North is the opposite – he disappears into society and then works undercover. What he and the rest of the team do is subversive, slick and fine. It couldn’t be more different, which has been a great challenge. It’s been a really interesting year.”