The idea that historians could use their knowledge of the past to advise useful courses of action for the future goes all the way back to Thucydides. “In recent decades, however, things have changed. The longstanding view of the historian as being, in modern jargon, ‘policy-relevant’, has fallen out of favour and often arouses suspicion” – within the discipline as well as outside it. Robert Crowcroft makes the case for a widespread revival of the approach now called “applied history.”