Lionel Murton

Two friends get drunk and decide to switch identities. One is a Parliamentary Secretary, and the other is the captain of a ship. 

In the early years of the World War II, the Royal Navy is fighting a desperate battle to keep the Atlantic convoy routes open to supply the British Isles, facing the great danger posed by the many German warships, such as the Admiral Graf Spee, which are scouring the ocean for cargo ships to sink.