“You’re a very good listener,” says the vacuous Polly to the arch manipulator Frances, in Lucinda Coxon’s gripping and joyful adaptation of Harriet Lane’s first novel, Alys Always, a preview of which we saw on Saturday afternoon. Polly doesn’t know the half of it; she has a great memory too. Frances has a gifted brain; in its deepest recesses she files away all the facts and feelings (names, passcodes, ages, hiding places for keys, etc) that she chances upon through everyday conversation that one day might, just might, come in useful. But does she use this gift for the greater good of mankind? Not exactly.

Frances is wasted in her day job – a sub-editor in the Books department at The Questioner Newspaper; in other words, a general dogsbody who spends her day feeding the meter for more senior employees’ cars, making the drinks for meetings, and hoping that the Departmental Head might one day remember her name. But a random experience changes all that. She witnesses a car accident late one night; she rushes to the scene to try to help but can only hear the accident victim talking to her from her trapped car. They have a brief conversation, where Frances does her best to calm her; but there’s nothing she can do apart from keep her company until the ambulance arrives. The victim is Alys – pronounced Alice – and she doesn’t survive.

But it turns out that Alys was the wife of Laurence Kyte, the most marketable thriller writer in town; and when the police suggest that Frances meet the family as part of a “closure” initiative, it’s probably an invitation she shouldn’t pass up. Particularly when it turns out that her boss is also at Alys’ memorial. Alys’ daughter Polly becomes especially attached to Frances; and as the latter’s influence within the Kyte family blossoms, so does her ability to spot personal opportunities that will do her no harm whatsoever, and her position in the office can take on a more significant role.

I haven’t read the novel, but it’s a truly engrossing and unpredictable story, with snappy, crisp (and sometimes excruciatingly wicked) dialogue, sparkling wit and a winning performance from Joanne Froggatt who introduces us, simple idea by simple idea, to the darker side of the unassuming office girl; so that we, the audience, don’t sit there tutting and criticising her devious planning, but in fact rather approve of how she tricks the foolish people around her to make a better life for herself. Morally we’re on very shaky ground here; but Ms Froggatt convinces us that it’s all just a bit of fun, and, if we were in her shoes, which of us would be that squeaky clean?

The blank wall that greets us when we arrive in the auditorium is used for various arty projection backgrounds, the majority of which quirkily suggest the location and/or mood for each scene so that we never need more than a few tables and chairs to be sure of our location. The mood is further enhanced by Grant Olding’s moving and haunting compositions, played live with style and panache by Maddie Cutter.

Robert Glenister is excellent as the morose and mournful Laurence Kyte, apparently plunged into emotional darkness by Alys’ death, although it’s not too long before he’s, shall we say, back to his old tricks. Ms Coxon has been generous with the script to Mr Glenister and he delivers some brilliantly sour one-liners and wallows in fabulous hypocrisy. I guffawed loudly at the observation about picking your way past the homeless to get to Hatchard’s before feeling incredibly guilty at finding it funny – ouch.

I really enjoyed Simon Manyonda’s arsy Oliver, the big-headed book reviewer who’s insufficiently aware of his own shortcomings; Joanna David’s calming but business-like Charlotte, the housekeeper-cum-literary agent with a guilty secret; Leah Gayer’s needy and irritating millennial Polly (a cracking West End debut that’s all character and no caricature); and Danny Ashok’s ever-hopeful but maybe too principled Sid.

There’s also a wonderful performance from Sylvestra le Touzel as Literary Editor Mary; like a cross between Rupert Murdoch and Margo Leadbetter, she bosses her underlings, but cultivates any story opportunity whilst always being seen to be On Top. She underplays the character’s savagery to perfection; and teases out riotous laughter when she offers Frances “flat white or latte… and a little pastry?” Those office politics and ingratiating tactics are so well observed.

But it’s Joanne Froggatt who carries off this superb play with a truly entertaining, insightful, comic and devastatingly ruthless performance. Her connection with the audience works incredibly well – she spends most of the play talking to us, so it’s no surprise that we’re behind her all the way – even when she’s forcing people’s hands and deliberately misleading them. What a little imp she is! Hugely enjoyable, beautifully written and structured, fantastic performances; an absolute gem. It’s only on at the Bridge Theatre until 30th March, but surely it should somehow have a life thereafter?

Production photos by Helen Maybanks