Sam Holcroft’s high concept comedy could use a rethink, says Bridget Galton.

In an arena overlooked on four sides, Sam Holcroft’s overlong high concept comedy about a horrendous middle-class Christmas is Ayckbourn meets Big Brother.

The set up, that each character’s coping mechanism – or rules for living - are writ large on illuminated boards, is a device with patchy effect depending on whether it feels contrived or rooted in recognisable behaviour.

So when Miles Jupp’s passive-aggressive prodigal son Matthew has to sit to tell endless lies to keep others happy, that knowledge ramps up the comedy. But when his needily exhibitionist girlfriend Carrie (Maggie Service) has to dance and sing to tell a joke, it’s just wearing.

More poignant is Adam’s (Stephen Mangan) trait of deflecting his failure and self loathing with funny voices and humorous name-calling in the face of his disappointed wife Sheena sipping wine while contradicting, and point scoring.

Holcroft is exploring Cognitive Behavioural Therapy – which she seems ambivalent about.

But like any therapy it’s all about the parents. Bullying controlling dad Francis and OCD Edith (Deborah Findlay) a crisply snobby bourgeois mama who descends into hysterical cleaning and swilling Solpadine in the face of family feuding, illness and infidelity.

Like the game they play in act two, where the ever-changing and secret rules make it impossible to play, we are often operating blind. But Holcroft says recognising our own traits can help us over-rule them.

It all ends in a farcical food fight, but farce depends upon careful pacing of hysteria, and Marianne Elliott’s production offers longeurs where smarter brushstrokes would have conveyed the tangled web of family relationships far quicker.

And while there are sharp jolts of comic recognition, there is also rampant overkill.

Rating: 3/5 stars