There are plays which leave their meaning open to interpretation, there are plays which stealthily declare their intent in a series of well-placed clues, and then there is The Speed Twins. No sooner has a question arisen in your mind ("Might this be some kind of queer gateway to the afterlife?"), it is answered, openly and definitively. "You're in Dyke Heaven, darling!" cries butch bartender Ollie as she welcomes twitchy, self-denying Queenie to a dilapidated supernatural version of London's covert Gateways Club, exposed in the film The Killing of Sister George. Gateways. Geddit? 

In fact, the Gateways is also a crossroads, a chance for Queenie to continue her fervent campaign of refutation or to embrace a second chance at life and love with old flame Shirley. In case we should be in any way unclear about which is the correct choice, prayer provokes mini natural disasters and the gradual acceptance of her true self is rewarded with champagne.

Anyone familiar with Chadwick's past projects (Bad Girls, Footballers' Wives) will know she has a strong aversion to both subtlety and subtext, yet there is something undeniably captivating about the bold, brash colours of her work as she swings wildly from operatic emotions and soap-opera clichés – yes, there are drinks thrown in people's faces – to deliciously catty one-liners and big belly laughs. The farcical touches give The Speed Twins a raucous energy and are juxtaposed well with the sombre beats.

However, this full-throttle approach also risks becoming wearing, more so in an intimate stage play than on a high-voltage primetime soap. Chadwick consistently scores on shock factor, hearty gallows humour and sweeping romance set to popular tunes, but seems worried she will lose us if she lingers too long on a more complex, quietly resonant note. Thus religion is passionately dismissed, identity debates reduced to box-ticking and simplistic labels, and the metaphysical elements hastily explained in reincarnation gags, grating supernatural effects and an unnecessary coda.

All of which threatens to stifle the genuinely moving drama and urgent, compelling debates at the heart of this piece. Chadwick offers fascinating insights into queer history and how social conflict shapes and distorts individuals, couples and families, as well as perceptively noting that sexual inequality might actually be eclipsed by gender inequality. Following Bridget Christie's Edinburgh triumph, the revival of Dusa, Fish, Stas and Vi at the Finborough and Blue Stockings at the Globe, this is truly the year of feminist theatre.

The Speed Twins touches on the courage it takes to choose a harder path, rather than accept a limited norm and a culture of deception, but the specific human experience of that is mainly recounted in bursts of exposition rather than effectively demonstrated. A shame, as the sterling cast copes well with the zigzagging tone and would no doubt have delivered with meatier drama. Amanda Boxer displays pin-sharp comic timing and unexpected vulnerability as Ollie, Polly Hemingway's Queenie is a commanding presence and Mia Mackie offers sweet support as Shirley.

There is no denying the infectious charm of this heavenly therapy session, nor the warmth of Chadwick's lovingly drawn characters. If only she would downgrade the proselytising and trust in the strength of her work to convey her message.

The Speed Twins, at Riverside StudiosMarianka Swain reviews The Speed Twins at Riverside Studios.3