Farmer Hector has fallen on hard times. The pigs and geese have been sold, his once robust vegetables are puny and small. Salvation comes from the rear end of a cow. Betty, an ornery beast much given to tipping her herd-mates, produces 24-carat poo.

Robin Hemmings narrates this fairy tale mash-up (The Goose That Laid the Golden Egg with hints of Jack and the Beanstalk, The Emperor’s New Clothes and a flash of TV series Hustle) to Anna Wheatley’s ukulele, squeeze box and cowbell soundtrack. She has a wonderful blues voice and the song Betty’s Got The Boos is an aural highlight.

Hemmings has a fine range of squelchy poo sounds and characterises a huffy cow with endearing enthusiasm. The audience participation auction, to buy the golden cowpats, ends only when the kids can’t think of any bigger numbers. And, thanks to a vote in which the kids unanimously support hard-up Hector in favour of the spiv who puts stars in Betty’s eyes, there is even a happy ending.

Pleasance Courtyard, 556 6550, until 27 Aug, 10.45am and 11.50am, £7–£8 (£6–£7).