It was the faded monochrome photograph of a small Black boy, both hands gripping a valise, as he leaves London with a party of other school-age evacuees, that caught the Oscar-winning filmmaker ’s eye while he was researching his ‘Small Axe’ film anthology. He tells Deadline’s Baz Bamigboye that image spurred him to create his deeply personal new film about the Nazis’ 1940 air campaign against England, which screens at the London and New York film festivals next month.