The essence of live performance is that every show is unique – with this bunch that is doubly so since they rely on the audience to guide them.

Indeed, here we have improv, the musical comedy version with not a note of the show created beforehand.

Many of us have seen the likes of Paul Merton & Chums on stage in this very theatre doing improv of the style seen on TV in Whose Line Is it Anyway, but even then there seemed to be well-rehearsed routines that somehow fitted into the requests.

This takes it to a whole new level with the Showstoppers company, a revolving cast of more than 20 performers and 10 musicians under the auspices of co-creator/director Dylan Emery, taking on the wide-ranging world of musicals.

They are, of course, fairly experienced at this – with 11 sell-out years at the Edinburgh Fringe, two critically acclaimed West End runs, an Olivier Award and a BBC Radio 4 series to their collective names.

Starting each performance from scratch and having to spontaneously create a brand new musical every night does have its drawbacks and quite possibly might mean that it could end up being the musical play that went horribly wrong…but it doesn’t.

Tonight was, obviously then, a premiere performance. There is a structure to all this – the emcee, needing to write a new musical in under two hours, asks the audience for suggestions about what it should be about, what type of shows might inspire the songs, and what it should be called.

This performance ended up, inevitably, being heavily influenced by the date – it being October 31. And so our five protagonists found themselves in a graveyard, on Hallowe’en, in a musical called Two Birds, One Tombstone.

Their musical styles chosen by the audience were not quite so obvious, being based around Joseph, Les Miserables, Bugsy Malone and, most unusually, Amelie – which at least proved that all suggestions, however obscure, are welcome.

Two forty-five-minute acts of the most perfect entertainment ensued, with the brilliance of this night’s five actors dressed in black, white and red - Ruth Bratt, Justin Brett, Pippa Evans, Joshua C. Jackson and Ethan Pascal Peters – accompanied by equally versatile musicians Craig Apps and Jordan Clarke.

As our musical progressed through teenagers Billy, Brad, Mary, Jo and Gary’s surreal and spooky night amongst the gravestones, accompanied by a menacing crow and visions of mortality, we witnessed a Les Mis-inspired soliloquy, a Joseph and the Amazing Technicolor Dreamcoat love song, a rap around a Ouija board, and a very apt side-step into a Rocky Horror themed number.

A fly on the stage (I’m convinced I’ve witnessed his cameo role in other recent productions) at one point even inspired a philosophical song full of insect metaphors.

Sometimes with improv shows it’s hard to fully relax as you wonder just how far the performers’ skills can stretch. Not with this lot – the audience were at all times utterly safe in the knowledge that there was no end to their talents and ability to spin rhymes, tunes, harmonies, dialogue and one-liners out of thin air.

True creativity and a fabulous night’s entertainment.