Green Wing and Free Agents star Stephen Mangan is to play the lead role in BBC4&#39s adaptation of the late Douglas Adams Dirk Gently&#39s Holistic Detective Agency. 　　Mangan will be joined by Darren Boyd as his sidekick Richard MacDuff and Cold Feet and Friends actor Helen Baxendale, as MacDuff&#39s girlfriend Susan. 　　Adapted by the Bafta-winning writer Howard Overman – who is also behind Misfits, Vexed and Merlin – Dirk Gently&#39s Holistic Detective Agency follows the exploits of Adams&#39s chaotic character as he uses his unusual methods to solve crimes. 　　Mangan said: &quotI&#39ve been a fan of Douglas Adams ever since the Hitchhiker&#39s radio series which I used to record as a child and listen to over and over again in my bedroom. It&#39s such a thrill to now be playing one of his brilliant characters. 　　&quotDirk is a chaotic, anarchic force of nature with a totally unique take on the world. He is described as &#39lazy, untidy, dismissive and unreliable&#39. I&#39ve absolutely no idea why they thought I&#39d be right for the role.&quot 　　The Dirk Gently books have formed the basis of a play and a BBC Radio 4 series but have never before been filmed for TV. 　　Adams&#39s agent, Ed Victor, said: &quotFor all the years I represented the late, great Douglas Adams, the most substantial frustration for both of us was that we couldn&#39t get films made either of Hitchhiker or Dirk. 　　&quotDouglas once said, memorably, that &#39getting a film made in Hollywood was like trying to cook a steak by having a bunch of people come into the room and breathe on it&#39. Well, we did eventually get a film made in Hollywood of Hitchhiker and, tragically, Douglas didn&#39t live to see it. Nor will he see this adaptation of Dirk – but it&#39s worth bearing in mind that Douglas always thought Dirk would make a better film than Hitchhiker and I feel sure that this new TV drama with a terrific script by Howard Overman will prove his point.&quot 　　Shooting begins this week in Bristol on the 60-minute drama, which is being made by ITV Studios in association with the Welded Tandem Picture Company. 　　The Dirk Gently production is to be directed by Damon Thomas – who also directed BBC4 drama The First Men in the Moon – and will air early next year.