Educated at Marlborough College, Ellwood joined the Royal Naval Air Service in 1916.
[1] During his service as a fighter pilot in the First World War, he scored ten victories (all in the Sopwith Camel) to become a double flying ace, being awarded the Distinguished Service Cross in the process.
[2] Having been awarded one of the first permanent commissions in the Royal Air Force in 1919, he was appointed Officer Commanding No.
[1] Ellwood served in the Second World War as Deputy Director of Bomber Operations before becoming Air Officer Commanding No.
18 Group in January 1943 and then Senior Air Staff Officer at Headquarters Coastal Command in March 1944.