Spinal Tap writer Christopher Guest confirms mockumentary series starring Chris O'Dowd The BBC Two series has been produced in partnership with HBO - the US cable network behind The Wire, Game of Thrones and The Newsroom. Guest, 64, will write, direct and appear in the show, which is currently in production and will air in Spring 2013. Family Tree stars O'Dowd as 30-year-old Tom Chadwick. Having recently lost his job and girlfriend, he is unsure of his identity. Upon inheriting a mysterious box of belongings from a great aunt he never met, he starts investigating his family lineage and begins a journey of self-discovery. The show has been co-written by Jim Piddock, who appeared in Guest's 2000 improvisational comedy Best In Show. It also stars Nina Conti - daughter of Scottish actor Tom Conti - as Tom Chadwick's sister Bea, and Tom Bennett, who appeared in Channel 4 sitcom PhoneShop. Guest said: "I am also delighted to welcome myself to BBC Television. I am very lucky to be working with an incredibly talented cast. Chris O'Dowd has been on my radar ever since he was a child actor in Wales. Chris O'Dowd added: "I'm terribly excited and monumentally under-qualified to work on an improvised show with Chris Guest. I call him Chris "cause we are friends. He calls me George. Previous BBC and HBO collaborations have included period drama Parade's End and lavish historical drama Rome.