Thomas, whose title will be creative director, joined Mr Smith in 2003, when it was known as Interfocus. He also co-founded Grey Desire in 1999.
In his new role, he will have day-to-day control of the creative department, with support from two other new creative directors.
Robin Garms has been promoted to creative director of interactive from senior art director. He replaces Jon Williams, who left to join Harrison Troughton Wunderman in January.
Schnoosee Bailey, also a senior art director, has been promoted to the new role of creative director of promotional marketing.
As well as continuing to oversee the agency's creative output, Cavers will help to develop Publicis Groupe's integrated offering.
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