Patti Harrison’s last London show, she tells us with concern, upset some audiences. So tonight she comes armed with a trigger warning. Cue a sequence cautioning us about the confronting topics Harrison is to address onstage, underscored by a series of inappropriate audio effects courtesy of our host’s sound-library sponsor. It’s a great big tease, of course, but – almost despite itself – works as a bona fide content warning, too, by exemplifying Harrison’s signature style (extreme earnestness as a prelude to something yelpingly silly) and previewing the brand of irreverence and provocation that characterises the hour to come. The conceit, in a show that recycles some routines Harrison performed at this venue 15 months ago, is that our host is working out material on the hoof, as a byproduct of her current “therapy journey”. Most of the jokes are prefixed by faltering monologues about Harrison’s pursuit of self-realisation, played with a wickedly straight bat. In her disaffected valley-girl drawl, they test our patience to breaking point – but are always redeemed by whatever wildly unexpected punchline or set-piece the Ohio native has hidden around the next corner. Sometimes, that’s a song: two standout numbers from her 2021 show, pastiches of Stevie Nicks and Joanna Newsom, are revisited. The latter, about an unlikely tryst with Steve Bannon, is the most rarefied of comic pleasures, not only for Harrison’s ridiculous (and spot-on) Newsom impression, but because of the daft, trance-like attitudes she strikes while delivering it. Elsewhere, the joke is to be found where the 32-year-old’s jargon-spouting, self-curating superego comes up against her violent, bigoted id – in anecdotes about her compulsion to kidnap her neighbour’s children, or in her monstrous outburst when encountering a pregnant women wearing – horror of horrors! – lipstick. You could extract from the show a satirical commentary on self-analysis as self-exculpation, on therapy as a get-out-of-jail-free card. But that would be to take it more seriously than Harrison is, or than its spirit of mischief and delinquency demands. If this gadfly comic wants to send anything up, one suspects, the notion that she be taken seriously would be high on the list. Patti Harrison is at Soho theatre, London, until 18 February