Long before the onslaught of reality television, Granada launched its pioneering Seven Up! series, tracing the lives of a disparate group of children every seven years from 1963. Using this concept as a starting point for fiction, Alexis Zegerman has crafted a fitfully entertaining, sporadically convincing comedy.

In a soulless television studio, we meet working-class Alan (David Kennedy), middle-class Tom (Jonny Weir) and upper-class Catherine (Susannah Harker), known as “princess” to the two men.

Anthony Clark’s production struggles with the fact that the actors look oddly unbelievable at all the ages they’re meant to be portraying, especially the two key points of 21 and 49. The more the timeline whizzes between these eras, the less we buy into the increasingly frantic parallels it tries to draw.

The initial set-up of the middle-aged trio glancing back over entire lives lived under television’s microscopic glare is ripe with potential, yet there is a growing sense that Zegerman doesn’t know where to go with her narrative.

Much as Catherine, Alan and Tom talk of marriages and jobs, we are not persuaded that these sketchily drawn characters actually have lives outside their seven-yearly trips to recordings. Their assertion that the programme is to blame for a panoply of ills appears even more unsubstantiated.

The actors work hard and Harker has a fine line in haughtiness, but Zegerman hampers them with her unlikely plot twists. The most intriguing person, disconcertingly, is the one we don’t see, namely the manipulative director of these documentaries.

Until 22 November (020 7722 9301,
www.hampsteadtheatre.com)