Stephen Mangan, star of BBC4’s Dirk Gently, talks to TV&Satellite Week about his love affair with the work of the late author Douglas Adams…

You’re a huge fan of Douglas Adams, and even appeared on Celebrity Mastermind answering questions on the author’s most famous work, The Hitchhiker’s Guide to the Galaxy. How did it feel winning the challenge?
“It was a beautiful, storming victory, the only thing I’ve ever won.”

When did you first discover Adams’ work?
“I listened to the original Hitchhiker’s radio series when I was very young. My English teacher said, ‘You might want to listen to the radio tonight’, and I was totally hooked. I have absolutely loved his stuff ever since.”

You’re back as private detective Dirk Gently for three new investigations, with Darren Boyd returning as your college friend Richard MacDuff. What can we expect?
“We have set up the agency together. MacDuff is billing himself as Dirk’s partner, while Dirk is billing him as his assistant, which causes a lot of tension. Dirk’s used to operating as a lone wolf, so to have MacDuff tagging along the whole time slightly throws him off his stride.”

It must be a big challenge adapting Gently for the small screen?
“The books are pretty unfilmable as written, but anyone who knows them well will recognise little references to things, which will hopefully keep the hardcore, diehard fans happy.”

How does your Gently compare with the character in the books?
“I’m younger, dress differently and not as pudgy as the Dirk in the books, but that’s all part of the process of making our version. He’s a hilarious character and I really enjoy playing him.”

He’s not the sexiest detective we’ve seen on TV, is he?
“Maybe it’s the suit, the hair or the car, but for some reason the ladies don’t usually come flocking. However, Dirk does find himself romantically involved, which isn’t something he’s used to.”

Gently’s car, a brown Austin Princess, certainly matches his unusual dress sense…
“As Dirk said in the pilot, all good detectives have a classic car. But I don’t think you could call this a classic – she handles like the QEII. I’ve decided to take Dirk’s driving skills up a level, so the car never pulls away without all four wheels skidding if possible, and never comes to a halt without a 20ft skid. Also, every time I get in it, I give it a kick. I’m amazed it’s still in one piece, and I have had a couple of the other actors screaming hysterically when I’m behind the wheel.”

He must be an interesting character to play?
“Dirk’s so mercurial, ranging from the ridiculous, petulant and crazy to quite straight and serious, and it’s nice to play a character who’s that liberated. He’s not one of those mean, moody detectives, with a difficult home life.”

He’s also quite brazen?
“I think I might have developed a touch of that during filming. For instance, I marched up to a man in the street who was carrying a lime-green briefcase and asked him where he got it, which is something I wouldn’t normally do. He was very sober-looking, and the briefcase just didn’t sit right with my inner Dirk. I suppose I was lucky he didn’t hit me with it.”

Dirk Gently screens on Monday, March 12 on BBC4, 9pm