Churchill sent Hess initially to the Tower of London, making Hess the last in the long line of prominent people to be held in the 900-year-old fortress.[43] Churchill gave orders that Hess be strictly isolated but treated with dignity.[44] He remained in the Tower until 20 May 1941. After being held in the Maryhill army barracks, he was transferred to Mytchett Place, near Aldershot. He was kept under close guard. Frank Foley and two other MI6 officers were given the job of debriefing "Jonathan", as Hess was now known. Churchill's instructions were that Hess be strictly isolated, and that every effort be taken to get any information out of him that might be useful.[45][46]
During his time as a prisoner of war, Hess was confined at Maindiff Court Military Hospital, Abergavenny, Wales, for treatment for insanity. He was treated well and enjoyed painting.