Alexi Kaye Campbell’s play of 2009 is based on two reliable dramatic conceits: the family reunion and a dinner that goes badly wrong. And true to that form much of the pleasure here lies in the trouncing of table manners. The main transgressor is Stockard Channing’s Kristin, an American-born British-based art historian who doesn’t suffer fools gladly, but does gladly eviscerate them with a barbed wit.

It’s her birthday and banker son Peter (Joseph Millson) has turned up for a celebratory dinner with his new girlfriend Trudi (Laura Carmichael) who is Christian and American much to the displeasure of Kristin, a communist, activist and 1960s protester who was, and is, proudly committed to her politics. In the eyes of Peter and his dysfunctional younger brother Simon (also Millson) she was more committed to politics and work than she was to them. Prompted by the new memoir of her “life and times”, in which her sons don’t get a mention, the boys finally confront Kristin about the mother-shaped hole in their lives.

Jamie Lloyd’s production ratchets up the tension to the reckoning. Channing is in commanding form as a woman whose apologia (the title of her book) is no apology for living the kind of life that men would never be asked to justify. Yet there are mis-steps that prevent Campbell’s play from joining the great family reunion plays of the past.

One of Campbell’s main points — forcibly put by Kristin’s gay friend and political comrade Hugh (Desmond Barrit) — is that the kind of political activism that defined his and Kristin’s generation could never be understood by today’s shallow and materialist lot, represented here by Simon’s soap star girlfriend Claire (Freema Agyeman).

Does that really wash in the age of movements such as Occupy and (although it had yet to emerge when the play is set) Momentum?

Although the conflict between God-fearing Trudi and rationalist Kristin is beautifully handled, the scene in which Simon confronts his mother with a childhood memory that illustrates the effect of her absence is, like many of the confrontations here, somewhat mannered.