Watching this new Christopher Guest sitcom is a peculiar experience. For example, the pieces to camera can look like a hackneyed device, worn out through over-use. But then, if Christopher Guest can't utilise pieces to camera from his characters, who can? For a particular kind of arch, absurd, self-aware comedy, he wrote the rulebook.

This feels like a very new venture for Guest. Not only is Family Tree his first TV project, but it's more plot-heavy and open-ended than his film work: the box of family treasures given to laconic lost soul Tom Chadwick (Chris O'Dowd) could be the passport to as much digression, misadventure and silliness as Guest and the cast fancy, as Tom follows his familial trail through Britain and America.

The Family Tree ensemble also contains Michael McKean, Nina Conti, co-writer Jim Piddock, Tom Bennett and eventually, such mainstays of Guest's films as Fred Willard. So, even if this opening episode feels slightly low-key, it seems reasonable to assume that we're in safe comedic hands.

Radio Times review

If you like the kind of amiable comedy that doesn't hammer every joke home, this could be for you. It's co-written and directed by Christopher Guest, who helped popularise mock-documentaries (This Is Spinal Tap, A Mighty Wind) and stars the excellent Chris O'Dowd as Tom, an unemployed 30-something who sets about tracing his family history.

Future episodes take Tom to America (HBO co-produces the series) but for now the action meanders around London, where Tom receives a case of family memorabilia from a great aunt and starts wondering about his ancestors. Was one a field marshall?

The plot is silly but in a confident sort of way: what other comedy would feature a character (Tom's sister) who expresses her deeper feelings via a ventriloquist's dummy of a monkey?

Chris O'Dowd brings his engaging brand of humour to the role of Tom Chadwick in this mockumentary from Christopher Guest (Best In Show, This Is Spinal Tap). When we join Chadwick, he's adjusting well to a life of 'wallowing' after being dumped by his girlfriend and redundancy from work. Then things perk up, after the sad demise of a great-aunt who leaves 'a little something' for him. Not, as it happens, a cash windfall but a tatty old chest stuffed with family knick-knacks that lead him on an ancestral adventure. With support from Nina Conti as Tom's sister, Bea, who lets out her inner voice through her ventriloquist puppet, Monkey.

This gently off-the-wall mockumentary marks the return, after a seven-year break, of Christopher Guest, the writer-actor-director responsible for [o]Best In Show[/i], A Mighty Wind and, of course, This Is Spinal Tap. This latest one features Bridesmaids and The IT Crowd star Chris O'Dowd, who plays a man tracing his family history. Mike McKean and Nina Conti (and Monkey) are his dad and sister; the latter was once sent to a therapist after a puffin touched itself inappropriately while looking directly at her. Glorious.

Chris O'Dowd Q&A

Chris O'Dowd talked to Sunday Mirror's Notebook magazine ahead of his new BBC sitcom.

Family Tree review

Perhaps Guest and Piddock fell into the trap of thinking that the naturalism of a mockumentary would take care of the comedy side of things, meaning they didn't really need to write any jokes?

Christopher Guest interview

Christopher Guest talks to Jay Richardson about his first TV series, Family Tree.

Chris O'Dowd and the rest of the cast talk Family Tree

It's the press junket to launch his latest show, Family Tree, but Christopher Guest has cried off sick, leaving journalists and cast to speak about him in the third person.

Family Tree review

Sure there are laughs and funny moments across the series but 'feel-good' is probably a better term to use than 'comedy'.

Chris O'Dowd interview

Bridesmaids, The IT Crowd and Family Tree star jokes he needs to push himself rather than push the luck of the Irish