It can be tiring traipsing around the annual Frieze London art fair in Regent’s Park – which is why, when you pass Tokyo gallery Taro Nasu’s booth, you may find yourself drawn to a black vending machine.

If you’re after refreshment, though, prepare for disappointment – because this automated device is an installation by British conceptual artist Ryan Gander, dispensing random artworks, at £500 a pop, instead of fizzy drinks.

Flash your credit card for this high-rolling game of lucky dip, and you could win a tiny “sculpture” embellished with a diamond.

More likely, though, the machine will spit out a black resin cast of a Casio wristwatch wrapped around a rock.

Other “prizes” include, in the words of an attendant, “natural stones” – which I think means, simply, “stones”.

Gander had wanted each artwork to cost £1,000. In the run-up to the fair, though, it turned out that the machine’s limit was much lower, so he settled on half that sum. A bargain, you might think. Still, when I visited, late on the fair’s opening day, only one person had opened their wallet – and their card was rejected.

This is the thing about Frieze: if you’re going to buy, you need a generous credit limit.