Powell, who has been with Profero since 1999, is promoted to the role from design and creative team leader.
Harrison departed to join another digital agency Reading Room, where he took up the post of communications director.
Profero has also promoted Chris Baylis, who is moving into a new role at the agency as creative communications director, and hired Fleur Davis as a designer. Baylis was previously senior copywriter at Profero while Davis joins from the BBC.
Wayne Arnold, UK managing director of Profero, said: "It is a really exciting time for Profero at the moment as we see the digital market continuing to grow. These two roles are simple -- to further improve our creative product and ensure that we are maximising the return on our clients' investment."
Profero has created campaigns for clients such as Ask Jeeves, Lufthansa and Singapore Airlines and is on the Central Office of Information's digital agency roster.
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