Phoebe Waller-Bridge in Fleabag
Phoebe Waller-Bridge in Fleabag
© Tristram Kenton

Poor Fleabag. She is a beautiful, well spoken, well educated wrecker, whose sexual obsessions and self-deprecating sadness seep into every nook and cranny of the lives around her, and mess them up just as badly as she fouls up her own relationships.

But that's not to say this isn't one of the funniest, filthiest and most disturbing shows you're likely to see, packed with dry humour and guilty laughs. The superb solo performance from Phoebe Waller-Bridge, who also wrote Fleabag, is an epic achievement, already acknowledged by its expansion into a six-part BBC series that plays something like a triple-X-rated version of Miranda. With its 'Let me tell you about me' premise, audience asides and a full supporting cast of tricky friends and relatives (including Olivia Colman and Bill Paterson), it's great TV.

But the bleakness of Fleabag's life, and the bitter consequences of her actions are painted with even greater intensity and pathos in this original stage piece, which previewed at the Soho theatre before becoming a huge Edinburgh Fringe hit in 2013. On stage, one chair and one striplight is all Waller-Bridge has to support her, but Fleabag's direct, intimate link with her audience means she's hiding nothing – but nothing – from us as she lays bare the details of her dysfunctional family, and the sexual encounters that leave her wondering if it's just her who feels out of control unless she's fucking.

Waller-Bridge is co-artistic director of new-writing theatre company DryWrite, together with Vicky Jones, who directs Fleabag with crisp assurance. The pair have experimented for years with throwing ideas at themselves and other writers, and challenging them to create a specific effect on their audience. One of Waller-Bridge's favourites is Funny/Not funny: how do you make an audience laugh in one moment, then feel something completely and profoundly different in the next?

She uses this effect to sneak up on her audience and surprise them, and achieves this time and time again in Fleabag, with the swift changes of mood punctuated by Elliot Griggs' subtle lighting, and smooth sound design from Isobel Waller-Bridge.

In fact, Phoebe Waller-Bridge is so good at flipping audience emotions that it can occasionally feel as if we're being played like fish on a line – but hey ho, it's worth it.

Fleabag is a masterly comic creation – a woman with an urge to splurge the intimate details of a disintegrating life. Waller-Bridge wants this story to reach into audience hearts. She succeeds.

Fleabag runs at Soho Theatre until 16 February.