Prest, who has been leading the agency’s creative department since Delaney Lund Knox Warren merged with Lowe last year, does not have another job to go to.
DLKW Lowe will now kick off a search for his replacement, however in the short-term the agency’s two deputy executive creative directors, Tom Hudson and Steve Boswell, will step up to take on Prest’s duties.
Prest began his career at Bartle Bogle Hegarty, before joining Lowe London as a senior copywriter in 2004.
He was promoted to creative director in 2008, but left the agency a year later to take on the executive creative director’s role at DLKW.
When DLKW merged with Lowe last July, Prest was appointed as the executive creative director of the new agency.
While at DLKW, Prest was responsible for overseeing new campaigns for Marstons, Halifax and Morrisons. During his career he has also created the "le sacrifice" ad for Stella Artois and the "anti-fit" campaign for Levi’s.
Greg Delaney, the chairman of DLKW Lowe, said: "We’d like to thank George for all that he has achieved here in helping to improve the standard of our creative output, firstly at DLKW and latterly through our merger with Lowe. We wish him all the best for the future."