Cyril Joseph Firth was born in Marston Magna, Somerset on 30 January 1901, the son of the Reverend Joseph William Firth and Alice Maude Firth (née Thring). He joined the Royal Navy in April 1919.  

After service in HMS ROYAL SOVEREIGN, HMS RALEIGH and HMS CONSTANCE, he joined submarines as a Sub Lieutenant in April 1924 and joined HMS K12 in November 1924. There followed appointments as First Lieutenant of H29 (December 1925) and L25 (August 1926), before a year in HMS HOOD from April 1927, followed by First Lieutenant of HMS OSIRIS in September 1928.

Following his Commanding Officers’ Qualifying Course, Firth took command of HMS H23 in February 1930. In March 1931, he joined the Staff of the Royal Naval College, Dartmouth, as a Lieutenant Commander. In May 1934, he took command of HMS L56, before being promoted to Commander in December 1935. Firth was then sent to the Far East to command the Destroyer HMS WESTCOTT, attached to the 4^th Submarine Flotilla in Hong Kong.  

Commander Cyril Firth died on 8 August 1938 in the RN Sick Quarters at Wei-Hai-Wei, North China from cardiac failure and pneumonia.  He was buried in the Royal Naval Cemetery in Lin-Kung-Tao in Plot 3, Row 7, Grave No 7.  He was the husband of Agnes May Firth and is commemorated on a brass plaque in the Wraxall Church in Somerset.