Dr Xand Van Tulleken and Raksha Dave investigate the smog that affected London in 1952, which is one of the deadliest environmental disasters 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.