His numerous credits include the character of Flying Officer Archibald Ives in The Great Escape, and Shughie McFee in the television soap opera Crossroads.
After briefly trying stand-up comedy on Scotland's variety circuit post-World War II, and service with Her Majesty's Armed Forces as a National Serviceman, after a period performing in song and dance, and comedy routines, in the English seaside towns along the South-East coast, he decided to become an actor, and took up a trainee position with the Perth Repertory Company in his early twenties, and went on to work with repertory companies in Oxford and Birmingham.
[3] Lennie's earliest major role was as Davie "Sunny Jim" Green in BBC Scotland's comedy series, Para Handy - Master Mariner in 1959–60.
Other TV credits include: Target Luna, The Saint (The Fellow Traveller), Doctor Who (in the serials The Ice Warriors and Terror of the Zygons), The Borderers, Z-Cars, Rumpole of the Bailey, Lovejoy, The Onedin Line, All Night Long, Keeping Up Appearances and Monarch of the Glen.
"[citation needed] Lennie's first role in cinema was in Tunes of Glory (1960), and he went on to establish a successful career in the medium as a character actor, often playing plucky wee Scotsman parts in war films such as The Great Escape (1963), 633 Squadron (1964), and Oh!