Christopher Haydon’s inaugural season at the Gate kicks off with Greyscale Theatre’s brilliant, dexterous examination of Julian Assange – a show that takes innovation as its subject. Actually, it’s mostly about French mathematician Evariste Galois (Jon Foster), who died in 1832 aged 21. He showed that equations of a certain complexity can’t be solved by their roots – also known as radicals. We need a new system. Enter Assange (Lucy Ellinson). 'Tenet' mixes two radicals – political and mathematical – and it’s the best kind of brain-ache. You have to sprint to keep up, but the result is a complexity unrivalled on the London stage.