‘Is that my gun?’

‘Yes, Jimmy, but I’m not going to use it. I’m going to kill you with my tongue…’

No, this isn’t the opening to an adult film. Or is it? This is the sound of the Cambridge Impronauts rehearsing for their new improvised show, iSpy: The ‘I’ is for Improv, that opens tonight at the Corpus Playroom. As I walk into the Larkum Studio the director, Ben Spiro, greets me by name. Without skipping a beat, the actors begin to incorporate a character called ‘Ted’ into the scene they are rehearsing. To them, everything is a prompt.

The sheer pace of the quick-fire improvisation is genuinely astounding – seamlessly switching between scenarios, characters, and accents. The chairs are laid out in a circle, and as the cast flit between roles, scenarios and locations, I can’t help but wonder – how do they do it?

“Beneath the surreal exterior there is a huge focus on craft”

The answer, it seems, is practice. Long before rehearsals begin on the show itself, there are several stages of warm up. Improv games abound. Some, frankly, were very odd – ‘Are we a cult?’ someone asks, after what had resembled a rain dance took place before me. I’m reminded of ‘whose-line-is-it-anyway?’, if all the producers of ‘whose-line-is-it-anyway?’ were on speed. Self-cannibalism, outer-space lovemaking, post-mortem structural engineering, bears with lasers on their heads, nuclear codes concealed in a pizza…

However, beneath the surreal exterior there is a huge focus on craft. ‘We world-build, we add significance,’ intones director, Ben Spiro, as the cast form an almost meditative circle. At the end of each round of improvisation, every ridiculous scenario is dissected: why were the nuclear codes in the pizza? What good will cooking the pizza do? Will the Canadian government send more laser-bears?

Although it is quite amusing to see a group of actors seriously discussing the finer points of nuclear codes that (presumably) come with garlic and herb dip, there is a clear point to all this. It’s all part of making people believe in the farce. ‘Don’t force it – connections will happen,’ Spiro adds, ‘Don’t make too many leaps or assumptions, make sure you have some checkpoints.’

Once rehearsals begin, it becomes clear that improvising an hour long show is no mean feat. Based on a single prompt – in this case, the spilling of a cup of coffee – and a location – in this case, the beach, there sprung a captivating tale of espionage, nudity, hydrophobia, tea made with lake water, and the decimation of Glasgow. Did I mention this was all improvised? I’d put a spoiler warning here but that’s the beauty of improvisation: your show will be completely different from mine.

The audience interaction comes from ‘interrogation’ sections in which you get the chance to channel your inner Benedict Cumberbatch and deduce who you think spilled the coffee. Or emptied the bin. Or unwrapped the present. You get the idea. It’s a very clever conceit, and one that has me listening intently to every detail in case I get the chance to quiz the characters on it later – and possibly blow the case wide open.

“I’d put a spoiler warning here but that’s the beauty of improvisation: your show will be completely different from mine.”

It’s clear that a lot of preparation has gone into this production, and I can only hope that audiences at Corpus Playroom are prepared for an evening in which anything – literally anything – can happen. If you’re looking for some light hearted procrastination, then this is shaping up to be one of the best ways to get it this term.

Before long, I get keen to join in. Until I’m actually asked to contribute. Fuck. Fuck. I’m in a room with potentially the most creative people on earth, and now I’m drawing a blank on ‘the most mundane act I can think of’.

Review: Hot Cross Men

The best I can come up with? Opening the cupboard. Great one, Ted. I’ll stick to a medium where I can draft and re-draft before publication, thanks.

iSpy: The ‘I’ is for Improv runs from the Tuesday 23rd – Saturday 27th May, 7:30pm, at the Corpus Playroom