London Under is a wonderful, atmospheric, imagina­tive, oozing short study of everything that goes on under London, from original springs and streams and Roman amphitheaters to Victorian sewers, gang hideouts, and modern tube stations. The depths below are hot, warmer than the surface, and this book tunnels down through the geological layers, meeting the creatures, real and fictional, that dwell in darkness—rats and eels, mon­sters and ghosts. When the Underground’s Metropolitan Line was opened in 1864, the guards asked for permission to grow beards to protect themselves against the sulfurous fumes, and named their engines after tyrants—Czar, Kaiser, Mogul—and even Pluto, god of the underworld. To go under London is to penetrate history, to enter a hid­den world. As Ackroyd puts it, “The vastness of the space, a second earth, elicits sensations of wonder and of terror. It partakes of myth and dream in equal measure.”