Lamb is to join one of JWT's clients, Diamond Trading Company, as worldwide marketing director, a role he will take up early next year. DTC is the company formerly known as DeBeers.
Before taking on his current post at JWT, Lamb had been the worldwide director of account planning at the agency for four years and, before that, global business director on DTC for five years.
His unrelated exit comes as it was revealed yesterday that JWT had appointed Toby Hoare as executive chairman, following last week's news that Simon Bolton is stepping down as its chief executive.
Hoare previously headed up the global HSBC business as chief executive of WPP's Team HSBC, an account he helped the WPP Group win.
Hoare will work alongside Craig Davis, JWT's worldwide chief creative officer, and Guy Chauvel, the newly appointed executive vice-president and director of multinational clients who has taken over from Lamb.
Bob Jeffrey, the worldwide chairman and chief executive of JWT, said: "We have benefited immensely, as have our clients, from David's razor-sharp insights over his longtime career at JWT. We will miss him, but we look forward to working with him in his new capacity at one of our premiere clients, DTC."
Lamb has worked at JWT for almost 20 years, having first joined in 1984 as a graduate trainee. In 1989, he became the youngest-ever board director of the London agency. In 1990, Lamb was promoted to director in charge on Kraft General Foods and then Kellogg. He went to AMV BBDO in 1994 to manage the Sainsbury's and Gillette accounts, returning to JWT two years later to become global business director on DTC.
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