Ronna & Beverly, Soho Theatre, London

Ronna and Beverly are Jessica Chaffin and Jamie Denbo, two American "thirtysomething" actors playing "fiftysomething" Jewish mothers who have co-authored abook of relationship advice called "You'll Do Better Next Time". But the duo aren't just self-help authors, they also fancy themselves as chat-show hosts and their guests have previously included Matthew Perry and Russell Brand. Matt Lucas is tonight's guest star and, though he has appeared before, his changeable expression seems to mirror the uneven ride that Ronna and Beverly take their audience on over the hour.

Constantly undermining and talking over each other, the pairing of Denbo's slightly hippy-dippy Beverly and Chaffin's rather static Ronna, which pays homage to Joan Rivers and Meryl Streep in The Devil Wears Prada, serve up some nice volleys amid some scripted and improvised plays that fall just outside of the laughter lines. "Gay women look like they could just turn up at your house and fix your sink," Beverly says, in their intro, contrasting lesbians, unfavourably, to their beloved gay male fanbase.

A small part Dr Ruth and a larger part Mrs Merton, the premise accommodates a running tension between the two but it's the tension between agony aunts and chat-show hosts that is most significant. The duo's "advice" remains largely shelved as they gossip about their lives. The more caustic Ronna proudly describes her son's Bar Mitzvah as "my day, of course", and Beverly's take on the destinies of her litter, or anyone else's, is to piquantly surmise "the pretty ones are our future."

As chat-show hosts they are hard to get a word in between, but when Matt Lucas has the chair we find out that he would have been an "emo" had he had hair as a teen. Meanwhile, the merit of Lucas's forthcoming voice role in the animated film Gnomeo and Juliet has Ronna doubtful : "I don't know how big your house is, but do you need a new kitchen?" Lucas is not to be outdone and says at one point: "I see some tension between you two, why don't you have a break?"

Time out to reassess this vehicle, warm and witty as it can be, certainly seems prudent.

To 9 January (0207 478 0100)