'The Skriker' had to cancel this week, raising the prospect of the Burton Taylor being briefly unoccupied. What to do to avert this tragedy? What play can be cast, rehearsed, learnt and mounted at three days' notice?

Cops & Robbers, the improv group, to the rescue.

All this three-strong team have to work with is the basic idea that they're putting on a musical. Beyond that, at the outset of the show, they clearly have no idea where they're going. There's no script, no roadmap to follow. The only vehicle they have is their trust in each other.

What more do you need? Answer: nothing. 'Spools' is fifty minutes of ephemeral joy built on nothing more than a genuine commitment to and confidence in improvisation. It was pretty sobering fighting through the queues shuffling into 'Mama Mia' at the New Theatre round the corner, on the way to the BT this evening. How much does that show cost to stage every evening? £30k? 'Spools' makes do with a few scraps of forgotten costumes left behind by some other show, and creates an evening of genuine, heart-warming comedy.

It's not just the off-the-cuff plot creation that makes it fun. It's the way the performers repeatedly try and wrong-foot each other, knowing they can deal with it. And it's the corpsing, as they see themselves going down improvisational dead-ends, knowing there's nothing they can do about it - and that ultimately it doesn't matter.

Will they become tomorrow's comedy stars? Will they become tomorrow's hedge fund managers? Who knows? But for four days they did a favour for another show that couldn't go ahead, and that gesture alone demonstrated exactly what makes them work as improv performers: generosity.

Last Spring, Cops and Robbers Productions, a student theatre company, put on The Improv Squeeze, an improvised rock musical based on the audience’s suggestions. The show was a sell-out success and was reviewed positively in The Cherwell (Oxford’s oldest student paper).

Now this Autumn, they take on another genre, with Spools: an Improvised Hollywood Musical, as part of Burton Taylor’s student season. The dual pleasures of improv, in my opinion, are on one hand marvelling at the quick wits and plotting of the performers and on the other, dissolving into laughter when the obvious cracks in the facade begin to show. Watching Spools’ opening night last night, I can see why Cops and Robbers has been so successful: the show masterfully straddles the line between impressive and a little bit stupid.

Improvising a whole, self-contained play off the cuff is already a mammoth task (one honed to perfection by groups like Austentatious, whom we reviewed last month) but creating a musical adds a whole other dimension to the proceedings. The group’s usual musician-in-chief, Max Blansjaar, was not available, so performer Leo Kitay does double duty as both a character and the soundtrack, effortlessly assembling perky piano numbers on a small keyboard.

In fact Kitay and Vicky Stone are the only returning cast members from the improv squeeze, with performer Lili Herbert also unavailable. Enlisting their friend Jake Dann, the three make a powerhouse trio, all the more impressive with the context that this isn’t their usual arrangement. From the minute the three bound onstage to perform a little warm-up jingle, genuinely mood-boosting and infectious silliness that feels as though your few pints deep into a catch-up with your goofiest friends. The musicality isn’t half bad either, with all three performers able to hold a tune, harmonise and revel in each other’s creative, off-the-cuff lyrics.

At the start of the show, audience members are given props - feather boas, a range of hats, a Santa dress from Ann Summers - to throw onstage when the mood strikes them. At first it’s slow going, but by the middle third items are flying onstage every few minutes, gamely incorporated by the performers. The never seen before (and never to be seen again) plot, built from a couple of audience suggestions is seemingly set mid-20th century, and focuses on a lawyer and struggling dog-groomer couple with six children to feed, a crooked business empire that’s determined to ruin them, and a fifteen-year-old kid who’s somehow become mayor of their town.

I’m delighted to confirm that while profoundly silly, it actually had a plot, with a beginning, middle and end. Clocking in at just under an hour, it had the audience in stitches throughout and could have easily been thirty minutes longer without losing anyone’s interest. But at five pounds a pop, this is still excellent value for a rousing evening that will delight everyone from college freshmen to their grandparents.

There’s a real warmth, energy and enthusiasm to the performances here. It was also impressively clean. Not, of course, that there isn’t a place for crass and raunchy jokes in improv, but bawdy innuendos can be low-hanging fruit. For that reason, it’s worth commending Cops and Robbers for creating a rare family-friendly show that’s no less funny for being so. Closing on Saturday, do your mood a favour and don’t miss it!