In his new role he will take the title of brand marketing and communications manager to help develop McCallum Layton's profile. McCambley left Nunwood at the end of last year.
Duncan McCallum, co-founder of McCallum Layton, said: "John brings a wealth of senior marketing expertise from both client and agency side to our company, and this hire matches our ambition in bringing some of the industry's best talent to our agency."
The agency has also hired Mark Gentry as a research manager. He was previously with Synovate and has 15 years' experience in the industry.