In September 1945, he was posted to Palestine with the 2nd Ox and Bucks and the rest of the 6th Airborne Division (see 6th Airborne Division in Palestine) during the Palestine Emergency. He returned to England and attended the Staff College, Camberley, in 1949. Tillett served with the 1st Oxfordshire and Buckinghamshire Light Infantry, 43rd and 52nd, from 1953 at Osnabrück, West Germany. In 1955 he became an instructor in the Nuclear Weapons Tactical Wing of the School of Infantry, Warminster, Wiltshire. He witnessed the British atomic weapons tests which took place at Maralinga in South Australia; the effects of which were to subsequently cause him health problems. In 1959 Tillett became second-in-command of the 1st Green Jackets (43rd and 52nd) based at Knook Camp, near Warminster. He was later posted to Uganda and became Commanding Officer of the 1st Ugandan Rifles, formerly the 4th King's African Rifles, based in Ginja, Uganda. One of his junior officers in the battalion was Idi Amin who was later to succeed Tillett in command of the battalion. Tillett, in the rank of local Brigadier, subsequently commanded the whole of the Ugandan Army. He later served in Ottawa, Canada and at HQ Supreme Headquarters Allied Powers Europe (SHAPE). He retired from the Army in 1969 and served as a Retired Officer mainly involved in officer recruitment for the Royal Green Jackets.