We were met at the door by a man in a lab coat and a red beret. “I've never done this show before. It's going to be a mess,” Portenza warned us, cheerfully. He wasn't wrong. This is very definitely a show in development – we were more focus group than audience, helping rate the jokes as they were made (and even providing a few of our own.)

If someone had told me what kind of show it was going to be – “he's got a few pages of things he wants to try out, and he's going to sort of mess around with the audience for the rest” – I'd have been extremely apprehensive. I've seen comics try that kind of thing before, and it's usually an absolute trainwreck – either hopelessly self-indulgent or cripplingly self-conscious. But Neil Portenza is no ordinary comic.

Two things make this show work: Portenza's openness to impulse, and his absolute commitment to following those impulses through. Don't be mislead by the chaotic presentation. It's impossible to pull off something like this without a huge amount of skill and experience – not to mention the sheer courage necessary to get on a stage with only the barest hint of a plan, trusting your instincts and the audience to fill in the gaps. Mention must also be made of the entirely improvised sound and lighting from the tech crew, which provided many of the highlights of the evening.

My job as a reviewer is complicated here. I can't tell you what the show's about, or what it's like, or even what's going to happen. But I can tell you that it was a highlight of the Fringe for me, and compel you with all my dubious authority to bring a willing, open spirit along to this glorious, glorious mess.