Born and raised in County Antrim, Northern Ireland, Lennox was inspired by cinema from an early age and began to make plans for a career as a filmmaker.
[2] In 2010 Lennox made his Television debut with a 30-minute drama, called Eclipse, starring Andrew Buchan.
[3][4] Lennox gained a place on the Master of Arts in Fiction directing-course at the National Film and Television School in Beaconsfield.
[2] Lennox's debut feature A Patch of Fog, starring Stephen Graham and Conleth Hill, was released in 2015.
[8][9] In 2017, 2018, and 2021 Lennox directed all three series of the Channel 4 television sitcom Derry Girls.