Marthe Mathilde Cnockaert, later Marthe McKenna, was a Belgian spy for the United Kingdom and its allies during the First World War.
She was born in a village to Felix Dnockaert and his wife Marie-Louise Vanoplinus. She began studying at the medical school at Ghen University, but her studies were interrupted by the outbreak of World War I.
She received honours for gallantry for her espionage work from the British, French and Belgians. A film of her first book I Was a Spy was produced in 1933.
She later became a novelist, and is credited with writing over a dozen spy novels in addition to her memoirs and short stories.
Some of her works include:
My Master Spy: a narrative of secret service (1936)
Drums Never Beat (1936)
Lancer Spy: a story of war-time secret service and espionage (1937)
Set a Spy (1937)
Hunt a Spy (1939)
Spying Blind (1939)
Spy in Khaki (1941)
Arms and Spy (1942)
Nightfighter Spy (1943)
Watch Across the Channel (1944)
Write Your Own Best-Seller (1946)
Three Spies for Glory (1950)
What's Past is Prologue (1951)