At 10.55pm on 24 April 1974, Portuguese radio played their entry to that year’s Eurovision song contest – and soldiers took to the streets. The tune by Paulo de Carvalho was the pre-agreed signal to start an armed coup, and for rifle-toting military to rise up against a fascist dictatorship. Citizens flocked to join in and there was so little resistance that flowers were placed in unfired gun barrels (it became known as the Carnation Revolution). It started Portugal’s transformation into a democracy and is surely the only revolution triggered by a crooner with a very large collar. If you...