 He returned to England to retire, but resumed working during the First World War as director of army priority at the War Office from 1917 to 1919, and then director of Disposal Board at the Ministry of Munitions.He was appointed a Knight Commander of the Order of the British Empire in the 1918 Birthday Honours for his services during the war.Henn died in a London hospital, age 74, after falling and breaking his thigh in two places and contracting pneumonia.