Stephen Sackur speaks to Marilyn Stafford, one of the great female pioneers of photo journalism. Early in her career she moved to Paris, where she became the protege of the brilliant Henri Cartier-Bresson and like him she loved to capture intimate portraits of ordinary people. Stafford has worked everywhere from war zones to cat-walks. Now aged 93, her work is being rediscovered by a new generation of admirers. Stephen asks - what gives her pictures their power?