Sofie Hagen, Soho Theatre review - sex weekend in Swansea, anyone?

Memory is a funny thing: it can get you through exams; it can comfort you or distress you; it can last a lifetime or go in an instant. In Sofie Hagen's case, her idiosyncratic one has provided material for her new show Bumswing, which started life at the Edinburgh Fringe and is now at Soho Theatre.

Bumswing, she tells us at the top of the hour with a deceptively sweet smile, is a departure from her previous few shows, which were about anxiety, abuse and self-harm (one of which, Bubblewrap, won her the Edinburgh Comedy Award for best newcomer in 2015). Her therapist told her to perhaps cut back on the trauma, so this hour is going to be fun.

The word bumswing concerns an incident from Hagen's childhood in Denmark; but as we'll come to learn her memory really can't be trusted (although her explanation of the word sounds so real about how children behave that I hope it's true).

Bumswing - through which Hagen meanders by guying vegans, talking about her allergy to strawberries and playing a terrific game of top trumps as she compares the UK's tradition-loving queen and the hip Danish one – mainly concerns her “sex weekend” in Swansea, “the Venice of Wales”, which promised so much but went downhill fast.

Those detours, which at first seem to be standard observational gags or inconsequential insights into Hagen's life, in fact turn out to be vital to the tale. Bumswing is a tightly constructed narrative where every detail eventually counts.

But Hagen is a unreliable narrator – she tells us so – and the way her mind works is to block out unwanted memories, or even nice ones if she's distracted by a fit bloke. So she relies on tiny prompts that her brain occasionally throws into her consciousness, to unearth bigger, darker episodes from her life, whether it's a school trip to a farm or that dirty weekend in Swansea.

Despite her protestations, it's often difficult to know how much is factual; we're used to comics embellishing the truth, or just making stuff up, of course, but some of the tales are so fantastical, you do wonder. Yet when a real-life trauma is mentioned – you sort of knew it was coming – you know it's true, and it's deftly handled.

This is a clever show rather than joke-filled, but it's well constructed, with lots of good callbacks and deliciously neat traps Hagen lays to upend us.

• Sofie Hagen is at Soho Theatre until 14 September; then touring until 23 May 2020
• Read more comedy on theartsdesk