Francis Lyall "Frank" Birch, CMG OBE (5 December 1889 – 14 February 1956) was a British cryptographer and actor.
During World War I, he served as a lieutenant commander with the Royal Naval Volunteer Reserve, and served in the Atlantic, the Channel and the Dardanelles before joining the Naval Intelligence Division (Room 40) from 1916 to 1919.
Birch wrote a satirical history of Room 40, Alice in ID25.
Birch left Cambridge to pursue an acting career in the 1930s, including the role of Widow Twankey in pantomime.
[2] In 1939, he was part of a BBC television production in a Teresa Deevy play "In Search of Valour".