He entered Britannia Royal Naval College at Dartmouth in January 1906.

[2] Horan entered the Royal Navy in 1910 and served in World War I[4] taking part in the Battle of Heligoland Bight in 1914.

[5] He was appointed Commanding Officer of the cruiser HMS Coventry in 1931,[6] Senior Naval Member on the Directing Staff at the Imperial Defence College in October 1935[7] and Commanding Officer of the battleship HMS Barham in 1937.

[6] He also served in World War II as Commander-in-Chief of the New Zealand Division from December 1939 to April 1940[7] before retiring in 1941.

[4] In early retirement he served as a staff officer in Combined Operations Headquarters in Richmond Terrace, London.