When John Robertson was at school in Perth, Australia, he was voted “person most likely to start a cult”. Well it looks as if his classmates were right. A couple of years ago Robertson was doing a stand-up gig and one night when things were not going too well he improvised a character, a floating lit-up head that would bellow demonically at the audience. It seemed to work. From there he created his video-game inspired show The Dark Room and a YouTube version notched up over 4 million hits. A cult was born.

Robertson has been doing his show in Soho at the Gem Bar over the last few months but I couldn’t make it, so he came to me instead. On a sunny Monday evening the curtains were closed and he performed a special edition  of The Dark Room in my lounge for three people. On Good Friday he is performing at the Udderbelly, a venue that holds 400 people. But that’s nothing. He has previously done it in front of nearly 2000 people in Perth, so the format is pretty flexible, but with the large audiences the aim is for it to feel like one is taking part in the world's biggest video game.

Here’s what happens. Be warned, there is a lot of shouting from Robertson, which might have been a problem for my neighbours but probably won’t be a problem at the Udderbelly. The set-up is like a very old eighties-style video game where audience members can do little more than choose from options on the screen (projected on the wall in my house, presumably on the stage on Friday). “You awake to find yourself in a Dark Room” we are told in a deafening voice as Roberton's face is illuminated from below by torchlight. I guess we have to get out. “Go north” “Sleep” “Turn the light on”. That sort of thing. Each option leads to a new page, a bit like a choose your own adventure story. 

I’d like to tell you more about the game but I can’t. Not because I’m sworn to secrecy, but because when I played it I didn’t get very far before I was killed. What I can tell you is that it is not like any other comedy show I’ve seen. I've seen interactive comedy before, but not in this format. I've never received a pithy put-down from a floating head before. Robertson is a very charismatic performer who is able to think on his feet – he has to because he doesn’t know what is coming next. He does seem to take rather too much pleasure in telling participants they are dead though. The killed-off competitors end up with prizes from hell. I got a rather disturbing stuffed toy. The others who played it chez Bruce got a tatty Star Trek paperback and a pair of purple children's Crocs.

With 400 people in the Udderbelly on Good Friday the chances are that some will get a few stages further than we all did. Comedian Brendon Burns is one of the few people to have got to the end of the game and beaten the Floating Head. Though as Robertson explains, he did it by going to the show over and over again and taking notes. Which is cheating really, but must be great for ticket sales. And Burns is not the only fan who keeps coming back. Determined punters will be coming on Friday who have already tried to beat the Floating Head during his earlier London run. As I said, a cult is born. 

The Dark Room is at the Udderbelly, SE1 on Friday. Tickets here. John Robertson will also be doing three shows at the Edinburgh Fringe in August – this, plus a stand-up show and a version of Hamlet with only three people in it. 

Click on "next" below on the right to watch a clip of The Dark Room.