When posted to Kabul, most people dress like they're on a mountaineering expedition. Rory Stewart, on the other hand, gets fitted out on Savile Row. Settling into a tattered armchair in the Afghan capital's Gandamak bar—named after the battlefield where British troops were defeated by the Afghans in 1842 during the first Anglo-Afghan war—the Eton and Oxford alumnus looks and sometimes sounds like an unreconstructed colonial nawab. He clasps his hands behind his head, exposing a pair of malachite cufflinks that glitter against gleaming white cuffs. "The secret to a good suit," he muses, "is using a heavy wool fabric. It...
