One-man fringe show invites people to feed their own cash through shredder to 'release them from the terrors of the financial system'

Some shows at the Edinburgh festival are daylight robbery. Some are cheap at the price, and some cost nothing. There is only one show at this year's festival, however, that invites members of the audience to come on stage and shred their banknotes. And the surprise of it is, people do it.

Gary McNair, a Glasgow-based theatre-maker, is the artist behind the one-man show Crunch, which runs until 27 August at Forest Fringe.

Conceived in the wake of the financial crisis, while McNair was an associate artist of the National Theatre of Scotland, the show seeks to critique money as a belief system.

In it, McNair promises a "five-step programme" to "release you from the terrors of the financial system". En route he takes in the history of monetisation, the notion of the collapse of trust in money (the bank run); and orchestrates a vigorous bidding war for an unspecified number of banknotes contained in a sealed envelope. Bids have, in the past, reached £100, although on his opening night in Edinburgh the bidding stopped at £26.50.

He also bartered with an audience member for her treasured necklace – her eventual price was a tour round Edinburgh, a bike ride, home-cooked lunch and the promise that he would come round and assemble her flat-pack furniture. Afterwards McNair said: "I wasn't expecting her to say she lived in Austria but if it's viable, yes, I will go to Austria and put up her shelves."

The climax of the show was, however, the moment when he suggested members of the audience feed their hard-earned cash through an office shredder, "as a vaccine against the disasters of the future, so that money and greed will lose their grip on you". Five did, with £10 notes as well as £5 notes returned to their owners as useless slithers of paper. (Destroying banknotes is not an offence, as commonly believed, though defacing them is.)

His research for the piece, he said, involved speaking to out-of-work stockbrokers about the nature of money and also attending a two-day motivational-speaking course. "I build a sense of trust between myself and the audience," he said. "I use the techniques of motivational speaking but I allow them to recognise that it's also a pastiche, it's not for real: but the rhetoric of it does have its own effect."

One of those who decided to shred, expressed no regrets after shredding £5 of the £15 in her pocket. "I thought hard about it, and I thought £5 was a price worth paying to experience what it felt like."