Born into a naval family in 1908, Geoffrey Bennett attended the Royal Naval College, Dartmouth and entered the service. After his promotion to Lieutenant he qualifed as a sigals specialist.He became Flag Lieutenant to a number of Admirals and in World War II he was first in Freetown, Sierra Leone, and then signals officer Force H in the Mediterranean where he earned the DSC.

He was promoted to Commander at the end of World War II. He then captained HMS St. Brides Bay in the Mediterranean Sea and then served in the Admiralty at Bath. He was promoted to Captain at the beginning of 1953 and then spent two years as naval attaché in Moscow, also covering Warsaw and Helsinki where he alerted the Admiralty to the potential growth of the Soviet navy. Retiring soon after returning to Britain he joined the household of the Lord Mayor of London and then, in 1960, became Secretary to the Lord Mayor of Westminster where he became an authority on civic protocol.

He always wrote and was awarded the Royal United Services Institution gold medal for an essay three times. At the end of WWII he published his first novel Phantom Fleet, a naval yarn under the pseudonym Sea Lion; as a serving officer he could not use his own name.

Over the next two decades he produced about twenty such novels for both adults and children and also wrote a number of radio plays for the BBC, including several serials for Children's Hour which featured the adventures of two Midshipmen, "Tiger" Ransome and "Snort" Kenton. Bennett's novels included theThis Creeping Evil, an allegory; The Diamond Rock, which was set in the Caribbean near Martinique during the Napoleonic wars and was based on a true incident; and The Quest of John Clare, about a family cursed over generations.

After retiring he took to naval history and under his own name published studies of the main battles of both world wars and Nelson, also a biography of Admiral Lord Charles Beresford, Charlie B and Cowan's War, an account of the British naval action in the Baltic in 1919 under Admiral Sir Walter Cowan which successfully thwarted the Soviet Union in Russia from seizing control of the three Baltic states, Estonia, Latvia and Lithuania. He was elected a Fellow of the Royal Historical Society.

He was passionately fond of the theatre and music and on his return from Soviet Union gave two long talks on the BBC's Third Programme on the Bolshoi Ballet which he had had opportunity to see in Moscow before they were well-known outside the Soviet Union.

After retirement he lived in Ludlow, Shropshire,in a 17th century cottage opposite an hotel where Nelson had once stayed. At the end of the 20th century there was renewed interest in his histories and most have been republished. Cowan's War was retitled Freeing the Baltic and has been translated into Estonian. Geoffrey Bennett died in 1983.

Details of his career may be found in Who Was Who and obituaries appeared in The Times and Daily Telegraph. A collection of his papers relating to his writing career is held by the Caird Library at the National Maritime Museum in Greenwich, numbered MS 85/098 and MS 85/132.