Most recently, Leonard was a founding director of ZenithOptimedia’s creative solutions team, working on a range of clients including British Airways, Zurich Insurance, O2 and Toyota.
UM London established the Ideation team last year to work in conjunction with strategy and planning, to inspire creativity in advertising strategy.
Headed by Andy Corcoran, the team services the agency’s clients such as Xbox, Microsoft and Brown Forman, and works with media owners including Sky, Channel 4, Absolute Radio and ITV.
Leonard will be responsible for working on multiple briefs across all agency clients.
Prior to ZenithOptimedia, he worked at creative agencies including the Triangle Group and CHJM.
Corcoran said: "We are delighted to appoint Nick at such an exciting time for our team. His experience and creative flair will add an extra dimension to the work we do for our clients."