Dr Xand Van Tulleken and Raksha Dave investigate the Great Smog of 1952 - the deadliest environmental disaster ever recorded and one of the world's worst peacetime catastrophes. Lasting just over four days, the Great Smog plunged London into a terrifyingly murky gloom - the acrid pollution seeping into homes, leaving Londoners gasping for breath, shutting down transport and emergency services, and overwhelming hospitals and undertakers alike.