Leslie was born in April 1924 in Poplar, London to Polish father Joseph Tennenbaum who worked as a ladies tailor, and Rose nee Silverstone and he had two older sisters and two step siblings from his father’s first marriage.

Leslie enlisted in 1943 and trained as a wireless operator and air gunner.

Lancaster PB570 of 1669 Heavy Conversion Unit departed from RAF Langar to carry out a night cross country operational training flight. Nothing was heard from the aircraft after take off and it did not return to base. The route was Base – Basingstoke – Barnstaple – Bude – St Mary’s – Bardsey – Aberystwyth – Northampton – Base. It was later recorded that the missing crew had lost their lives at sea.

F/E, Sgt Gerald Frederick Arthur Clapton, 1605772
A/B, Sgt Henry William Nevil Drawbridge, 1804021
Nav, Sgt Roy Holmes, 1676657
R/G, Sgt Eric Durham Keeling, 1899507
W/Op, A/G, Sgt Leslie Marcus Tannen, 1891873
MUG, Sgt Peter Hadrian Voller, 3025347
Pilot, F/S Ian Albert West, RAAF, 427274