If you drink the water in Ciudad Juárez, there you’ll stay, goes the saying – Se toma agua de Juárez, allí se queda. It’s not a reference to the quality of drinking water (about which polemic abounds because it is so dirty) but to the beguiling lure of this dusty and dangerous yet strong and charismatic city. It’s a dictum that might be applied to the whole 2,000-mile Mexico-US borderland of which Juárez and its sister city on the US side, El Paso, form the fulcrum.

Ten years ago, I returned from several months’ immersion along that frontier, reporting on a narco-cartel war for this newspaper and eventually writing a book, Amexica, about the terrain astride the border, land that has a single identity – that belongs to both countries and yet to neither. A frontier at once porous and harsh: across which communities live and a million people traverse every day, legally, as do hundreds of millions of dollars’ worth of goods annually.