My husband and I are fully signed up Harry Potter geeks so were intrigued to see Friday's performance in Blackwell's: The Show That Must Not Be Named. I must state upfront – as did our host, Harry Househam, that the show is not at all, in any way, affiliated with J. K. Rowling, or Warner Bros or the actual Harry Potter. It is an improvised parody performed by an energetic troupe of five young actors who take ideas that have been written down by audience members and added to the Goblet of Fire to aid the creation of a new 'Harry Potter and the...' type story, depending upon the idea.

I was pleased to see the bookshop filling up nicely as we made our way to the 'bar' (fabulous - £2 wine – thank you very much Blackwell's Bookshop in the Westgate!) and there was a pleasant atmosphere humming through the mix of families, friends, students and couples attending. I'm always nervous that the sometimes-reserved British audience won't be responsive to this sort of show – joining in and throwing out suggestions – but I had nothing to worry about on Friday. We were given a brief five-minute warning and then the troupe bounded out onto the 'stage' (we were in a bookshop, don't forget). With a backdrop of floor-to-ceiling bookshelves scattered in Potter-posters and a trio of huge Potter-esque trunks (suitcases, not swimming shorts, that would be weird even for improv) I found it easy to ignore the real world for an hour or so and lose myself in the madness of Tight Five's imagination.

Houseman's hosting was brilliant - energised, fun and funny. We were thrown straight into a bit of an improv 'exercise' for his four Hogwarts students, where they had to carry on telling the story, without too much hesitation, while incorporating whatever ridiculous scenario or item was thrown into the mix from the Goblet. Or without using the letter S, for example. The audience joined in the joyous killing ('Avada kedavra!') of each student as they failed to meet the requirements of this exercise. Think Just a Minute, but in cloaks and with wands. And magical death. The kids in the audience were loving it. I include myself in that category for this particular show.

The main part of the show began with an awkward 'who in the audience gave us this idea' moment, which is what gave us the title of our performance 'Hannah Why and the Hipster Coffee Shop'. Hannah was happy to admit to the hipster coffee shop idea (and why not, it's a mine of fun-poking joy!) but when asked for her surname only answered with 'Why?!'. So our troupe just went with it and came up with a mad, rambling but clever and hilarious tale which began with a house-elf and a half-troll called Tomothy drinking fancy deconstructed coffee while not declaring their love for each other. We were then treated to a tri-wizard tournament presented by Barty Crouch Sr (a snooty Dom O'Keeffe) with a sylph-like Beauxbaton student, (played with all the stereotype stops pulled out by the hilarious Ed Scrivens) a meat-head Durmstrang student called Oliver Lightly Soiled Snow (an impish Francesca Forristal) and the very hipster Hannah Why played very cleverly by Vicky Hawley, especially amidst confusion surrounding whether it was her daughter (Hannah Jr, of course) who was entered into the tournament, or herself (she managed to play both roles). And every role in between filled by whoever wasn't on stage at that moment.

I laughed my flip-flops off and went straight home to watch a proper Harry Potter film. It was good, definitely more coherent, but nowhere near as funny as The Show That Must Not Be Named. I look forward to seeing more from Tight Five and Comedy in Oxford soon.