He served in the Royal Army Medical Corps during World War I and World War II and served as the director of medical services for the Allied Forces in North Africa from 1942 to 1944.

[4][2] From 1914 to 1918, during World War I, Cowell served in the Royal Army Medical Corps.

[2] From 1939 to 1946, during World War II, he served again in the Royal Army Medical Corps.

[1] From 1942 to 1944, he served as the director of medical services for the Allied Forces in North Africa.

[2] In 1944, he was appointed as an honorary surgeon to King George VI, a position in the Royal Household.

[2] He was created a Commander of the Most Excellent Order of the British Empire in the 1939 Birthday Honours.