After about three weeks of shooting, Noël Coward realized that (a) Sir David Lean knew a lot more about filmmaking than he did, and (b) he didn't care much for the long hours. So Coward effectively handed the directorial reins over to his partner at that point.
There were doubts as to whether Noël Coward could convincingly portray a hardened Naval Commander. After the movie's release, his performance was widely praised.
Noël Coward was a friend of Lord Louis Mountbatten, who was Captain of the Royal Navy destroyer H.M.S. Kelly from the outbreak of World War II until the Kelly was sunk by enemy action in May 1941. Coward wrote the screenplay for this movie based on Mountbatten's experiences on H.M.S. Kelly. Coward's character in this movie, Captain E.V. Kinross R.N./Captain "D", was also based on Mountbatten's experiences.
Noël Coward was nervous at the prospect of directing and asked his friend Sir John Mills if he could recommend someone to help him. Mills suggested "the best editor in the country", Sir David Lean.
Before accepting the assignment, Sir David Lean asked Noël Coward how the credits would read. Coward suggested that they would say "helped by David Lean", but Lean insisted that they read "Directed by Noël Coward and David Lean". It was his only request, and one to which Coward readily agreed.