Family Tree follows the world and journey of 30-year-old Tom Chadwick. Having recently lost his job and girlfriend, Tom has a rather unsure sense of his own identity. But when he inherits a mysterious box of belongings from a great aunt that he never met, he starts investigating his family lineage and uncovers a whole world of unusual stories and characters and a growing sense of who he is and who his real family are.

Family Tree is a single-camera, improvisational, mockumentary comedy, a style that Christopher Guest's films have pioneered in the past.

BBC commissioner Janice Hadlow says: "I am delighted to welcome Christopher Guest to BBC Television. It will be his first television series for British audiences and one I am proud to have here on the BBC. It has a stellar cast led by the fantastic Chris O'Dowd and is an exciting collaboration with NBCU International and HBO. Family Tree will form a key part of the channel's comedy next year."

Christopher Guest says: "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 adds: "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."