One has only to glance at the map of the Paris Métro to evoke a memory of the smells and noises in that confusing maze of lines and stations. The sound of the buzzer just before the doors close, the mixture of residual soot, cleaning fluid, Gauloises (no more), and often comfortingly warm air, all combine to win the traveller's affection. After a while you learn to try to avoid changing at Châtelet (better to get out and walk). It took the authorities decades to change the name of the Louvre stop, so that tourists ceased getting off there – only to find the museum entrance was half a mile up the road. (Palais Royal–Musée du Louvre is the correctly named one now.)

What, though, of those mysterious names that adorn dozens of stops? Who, what, were they? Some are battles – Austerlitz, Iéna, Bir-Hakeim, Wagram. A few authors have their own stations – Emile Zola, Voltaire, Goncourt, Anatole France – but who knows readily of La Motte Picquet–Grenelle, or Malakoff–Plateau de Vanves,