Horner, who joins Lucky Generals on 2 March, will work initially across all of the agency’s accounts, reporting to the co-founder Andy Nairn.
Horner was most recently a freelance planner. As a strategist at Mother, he was promoted alongside Matt Hardisty (now a partner at Jam) to joint head of strategy in 2011. He left the agency in December 2013 after five years.
Nairn said: "Loz is an outstanding strategist. Very commercial, brilliantly creative and a lovely guy to boot. We’re growing in leaps and bounds, and Loz will make us better as we do so."
Before Mother, Horner worked at Wieden & Kennedy in Amsterdam, and Leo Burnett and Carat in London. He has won Account Planning Group awards for clients including Coca-Cola, Nintendo and Stella Artois. Horner also picked up a bronze IPA Effectiveness award for Boots in 2012.
Lucky Generals has recently added Pot Noodle and Hostelworld.com to its roster of clients.