Lucas has spent the past five years working on numerous PHD accounts, such as BBC and Prudential, and helped plan the launch of eBay's first UK advertising at the end of 2004.
Prior to this, Lucas worked as a strategist for Carat Insight.
Dr Wayne Fletcher, head of Carat Deepblue, said: "It is enormously exciting to be working with Leo again. He brings a wealth of experience and will help ensure we place strategic thinking at the very heart of what we do."
Lucas added: "My task is to help brands to establish more engaging relationships with consumers."
Carat Deepblue is the strategic communications of the Aegis-owned unit that was first established in November 2003, and has offices in Milan and Paris.
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