After finishing Special Operations Executive (SOE) signals training school in September 1943, he was part of a three-man team parachuted into occupied France in June 1944.

Leney (codenamed "Jeremy") was the radio operator of his team, whose other members were the English-speaking Captain Geoffrey Hallowes and the French-speaking Lieutenant Henri Charles Giese.

He remained with her to make radio contact with SOE headquarters, while Hallowes and Giese sought out local resistance fighters.

Leney established successful radio contact with SOE/HQ and some thirty (30) containers of arms were dropped to equip the FFI to engage detachments of withdrawing German troops.

[1][2] His previous mission in France having ended in September 1944, Leney was parachuted into Burma on 15 March 1945 with a team from Force 136, an arm of SOE operating in South East Asia.