Schurch's father was Swiss but living in London when he was born at Queen Charlotte's Hospital. During his late teens he was a member of the British Union of Fascists. On July 8, 1936, Schurch enlisted in the British Army as a Royal Army Service Corps driver.
In June 1942 Schurch was captured by the Germans in Tobruk and began a career working for both Italian and German intelligence. Often he would pose as a captured prisoner-of-war to gain the trust of fellow Allied prisoners, including Colonel Sir David Stirling, founder of the Special Air Service.
Schurch was arrested in Rome in March 1945 and tried by Major Melford Stevenson in a court martial convened at the Duke of York's Headquarters in Chelsea, London in September 1945. He was found guilty of all ten charges against him: nine counts of treachery under section one of the Treachery Act 1940, and one charge of desertion.
Theodore Schurch was hanged on January 4, 1946 at the age of 27. His hanging took place at HM Prison Pentonville, and was conducted by Albert Pierrepoint. Schurch was the only British soldier executed for treachery in the Second World War.