Legend has it that the ancient Greeks Zeuxis and Parrhasius once held a competition to establish who was the better painter. Zeuxis unveiled a painting of grapes so realistic that the birds flew down to peck at them. Zeuxis, keen to reveal Parrhasius’ painting, grasped at the curtain, not realising that it too was a painted illusion. The story offers us a means to navigate this year’s Jerwood Drawing Prize.