With Antony Gormley’s unsettling South Bank rooftop sculptures currently demonstrating all that is good about public art, it’s time to take a look at all that is bad. Really bad. Step forward the Potters Fields Park Festival, which takes place on an site overshadowed by Ken Livingstone’s City Hall eyrie which has been remodelled under the mayor’s 100 Public Spaces programme. Featuring the joys of ‘Compost Mentis’, a show featuring, you guessed it, a compost heap, and ‘Scarabeus’, a poetry performance inspired by newly planted cherry trees, the event, from 17-19 May, looks set to be a feast of toe-curlingly awful performance and installation. Astragal is packing the picnic hamper.