One winter’s day almost 90 years ago, the Hungarian-American photojournalist Robert Capa paused on a street in southeast Madrid to take a picture that would echo around the world and down through the decades.
In it, three children sit on a rubble-strewn pavement in the working-class Vallecas district of the Spanish capital. Behind them squats a plain, single-storey house pitted with the shrapnel of a fresh bombing raid.
