Born Joseph Anton Richlé on 22 May 1919 to Swiss parents, he reportedly visited Germany in the late 1930s and attended a Nationalist Socialist rally at Nuremburg after which he became very anti-Nazi.
In July 1939 he joined the British Army having changed his name to Leslie Gilbert. Like all those of foreign descent he was restricted to joining the Pioneer Corps but, being fluent in five languages (English, German, Swiss-German, Italian and French), he transferred to the Intelligence Corps.

In 1944 Sergeant Gilbert volunteered for special duties and on several occasions he attempted to penetrate German-held territory dressed as a German soldier to gather information at great risk to himself as, had he been captured, he would have been shot as a spy. He was awarded the Military Medal (MM) for one such action, his being one of only six MM’s awarded to members of the Intelligence Corps during the War.

His medals are, from left to right; Military Medal, 1939-45 Star, France and Germany Star, Defence Medal, War Medal.