In the quiet Cotswolds village of Great Rollright in 1944 a thin and unusually elegant housewife emerged from her cottage to go on her usual bike ride. A devoted mother-of-three attentive wife and friendly neighbour Sonya Burton seemed to epitomise rural British domesticity. However rather than pedalling towards the shops with her ration book Ursula Kuczynski - codename Sonya - was heading for the Oxfordshire countryside to gather scientific secrets from a nuclear physicist. Secrets that would enable the Soviet Union to build the atomic bomb. In Agent Sonya Ben Macintyre reveals the astonishing story behind the most important woman spy in history and the huge emotional cost that came with being a mother a wife and a secret agent at once.