Spinal Tap's Christopher Guest making new documentary-style comedy series starring Chris O'Dowd

Co-created by Guest and British-born actor/writer Jim Piddock, Family Tree will star O’Dowd as a 30-year-old called Tom Chadwick who’s recently lost both his job and his girlfriend.

Faced with an identity crisis, and suddenly left with nothing to do but investigate a mysterious box of belongings bequeathed to him by a great aunt, Tom begins to trace his family lineage and uncovers a whole world of unusual stories and bizarre characters.

Joining O’Dowd in the show’s cast are Nina Conti, who’ll be playing Tom’s sister Bea, and Phoneshop’s Tom Bennett as his best friend Pete. Family Tree will also feature Ed Begley Jr., Maria Blasucci, Matt Griesser, Don Lake, Michael McKean, Lisa Palfrey, Amy Seimetz and Fred Willard, with Guest and Piddick making on-screen appearances throughout the series too.

Perhaps inspired by shows like Curb Your Enthusiasm and The Thick of It, Family Tree will be a single-camera, improvisational, documentary-style comedy. The series is being co-produced by the BBC and HBO, and shooting is due to continue until early 2013.

Talking about Family Tree with his tongue in his cheek, Christopher Guest joked: “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 ‘coz we are friends. He calls me George. I don’t know why.”

Family Tree, which BBC2 Controller Janice Hadlow says “will form a key part of the channel’s comedy next year” is due to air in the UK in spring 2013.