You’re facing 20 complete strangers in a stage-lit room that once housed an old post office.

Mild feelings of trepidation and nerves mix with the excitement about the uncertainty of a beginners’ improvisation and actor’s comedy course. There’s no reception or idea of who’s in charge when I arrive, are we all leading the group? What is actually going to happen here?

Fortunately, the leader of the course, Luke Marquez, steps into the centre to bring some sort of direction to the bemused and half-blushing faces beginning to fill the room.

He takes us gently into some warm-up exercises and the obligatory ice-breaker of introducing yourself with an interesting detail. Apparently you can get a hedgehog embedded in your leg, which was in a whole other league to my “Hi, I’m Sid and I have unusually hairy ears”.

After everyone is acquainted we do loops around the room following Simon-says-like instructions from Luke who seems intent on making us feel as silly as possible, breaking down the usual social norms of not hugging a random person and pretending to be penguin huddled in a blizzard.

Then things really get interesting. The group is instructed to develop a walk while re-thinking their relationship to the ground. For some reason I can’t help thinking about the floor becoming jelly. As I walk forward I imagine an orange film covering the entire room. Then we’re told the physical ground beneath us is beginning to travel up our body.

Starting with my legs, I willingly move them as if made of jelly and begin prancing around the room like a maniac. As the imaginary sensation travels up my body – on the instructions of our giddy leader – I step into a new body resembling Mr Tickle and am slowly absorbed into a whole new wobbly existence of my own making.

I see 20 other people imitating what looks like the Monty Python silly walks sketch. The creations of the group all run on their own internal plane. Some amble and shuffle along like a zombie dragging a wounded leg across the floor, others gracefully float and make figure of eights, gentle stepping in between the marauding figures, one aggressively marching with a military-like thousand-yard stare.

The characters begin to vocalise themselves and suddenly the room is echoing with what can only be described as a chorus of the temporarily insane. Fully immersed in their new characters, participants begin talking and interacting completely off-script. There’s odd-sounding hellos and general musings about the nature of man. “Is that cheese you can smell?” one uppity-looking gentleman asked me.

Half of your brain is willing to go along with it while the rational side tries to jump in. “Er, No it isn’t,” I manage to protest in my best Mr Tickle impersonation. “I’s delicious chocolate cake.” Thankfully we continue walking past each other before I have to come out with something else.

We pause for a break and return to normality for five minutes. At this point I feel like I know everyone in the room intimately but still can’t find the words to have a normal introduction after what we all just went through.

The second half sees the characters we’ve created put in different scenarios. Half the room performs while the other is now watching. I line up with the other ambling figures and pretend to walk to a bus stop in character. As I start walking the nerves get to me and I half-forget what I’m supposed to be doing. I reach the imaginary bus stop and gaze at others, waiting for a cue from someone I can respond to.

Luckily others are well ahead of me, some begin chatting, one chronically happy character lets out an excuse to leave the scene: “I’m so happy! My Dad just phoned, and he said he’s going to die so I must be going.”

Luke then splits us up into three groups to improvise a scene where we are all waiters trying to move some boxes. Such a simple instruction soon ends up with my two companions, one of whom decides to be Mexican, throwing a box of imaginary tacos at me like a kind if human taco dartboard. I collapse on the floor not knowing how to take the scene any further. In my death throes I call out for my anti-taco medicine.

Next we’re handed a brief to become incompetent cat burglars to do in front of the rest of the class. I rack my brains for a formula to use for a character. I could do a good Burglar Bill impression, but I opt for an East End alcoholic called Ronnie. As we begin there’s a pause, I try to read the other person’s actions but don’t want to take over the scene too much. I introduce my character and do my best Cockney accent: “Let’s ‘ave some drinks then.” To my relief the others go along with it, we do some shots and drink to the magnificent burglary we’re about to do.

We manage to climb over a wall getting progressively more drunk. Once over the wall though we all seem at a loss of where to take the scene. My fellow burglar breaks his arm trying to climb up what I guess was a wall into a house, but to my annoyance I can’t seem to grasp the moment and work it into the story. In a flurry one of us decides to end the scene abruptly by shooting the others and running off with the swag. The scene ends and I jump up from the floor and return to my normal self.

n Sid's course was run by the Shoebox Theatre at their premises in Theatre Square, Swindon. For more, see www.shoeboxtheatre.org.uk