Career
He became a full-time professional writer in 1932. Before the war he was a novelist, travel writer, critic and broadcaster. He was in the Royal Air Force from 1940 to 1948, as a staff officer in Fighter Command to 1944.
He worked in the Fighter Command Headquarters underground operations room, and handled classified Ultra material from Bletchley Park.
He assembled information about German long-range weapons, going to France and Belgium in late 1944 to investigate captured sites. From 1944 to 1945 he was at Supreme Headquarters Allied Expeditionary Forces headquarters in Versailles.
At the end of the war in Europe he was appointed Air Historical Officer, Fighter Command. After leaving the Royal Air Force in 1948 he went to the Cabinet Office as a historian, and wrote the official history The Defence of the United Kingdom.
Giving his address in the prreface as Falmer, Sussex.
Since 1957 he has been a free-lance writer on military topics. His books Barren Victories and The Lion and the Eagle emphasize the importance he saw in the “Anglo-Saxon” alliance of Britain and America. A review by Robert Blake of a later biography of Sir Henry Wilson said that Collier’s attempt to rehabilitiate Wilson in his 1961 biography Brasshat carried little conviction because of his uncritical admiration for Wilson.