Thomas, who left Saatchis in 2001 when he stood down as CEO of Saatchi & Saatchi Japan, will take on the role of head of communications and media to spearhead growth of Dunnhumby's multimedia and creative capabilities.
Thomas spent 18 years at Saatchi & Saatchi, where he held key global roles, including vice-chairman of the UK office, regional director of Asia/Pacific, chairman and CEO of Saatchi & Saatchi and Zenith Media Singapore.
At Dunnhumby, he will be responsible for driving its creative and multimedia communication services in the UK.
Dunnhumby hopes his appointment will help redress how people see the consultancy, which is best know for its database and customer insight activity.
Edwina Dunn, chief executive of Dunnhumby, said: "For the past few years, we have been developing an integrated communications and media capability that enables our clients to connect more effectively with their customers through relevant communication. Clients are demanding better targeting and real accountability from their marketing communications and Dunnhumby is in an industry leading position to deliver this".
Thomas added: "It was a simple decision to join Dunnhumby. I want to be part of creating the marketing company of the future -- a vision embraced passionately by Dunnhumby as it is currently in a unique market position to do so."
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