Was head of code development and code security for the Special Operations Executive (SOE). The SOE was reponsible for supplying and coordinating resistance activities against the Axis powers during WWII.
Was the son of the owner of Marks' bookshop as featured in 84 Charing Cross Road (1987).
Leo wrote the "code poem" used by Violette Szabo as portrayed in the film Carve Her Name with Pride (1958). Leo was a real wartime cryptographer and often composed poems like this for agents to use as an emergency code. The life that I have Is all that I have And the life that I have Is yours The love that I have Of the life that I have Is yours and yours and yours A sleep I shall have A rest I shall have Yet death will be but a pause For the peace of my years In the long green grass Will be yours and yours and yours
He was awarded the MBE (Member of the Order of the British Empire) in 1945 for his wartime work with SOE.
His body was donated to University of East London for medical science.