Harrison is the most-awarded creative director in direct marketing since the Lions Direct launched in 2002.
HTW won the inaugural Lions Direct Grand Prix. And, in the four years since, it has won three gold, five silver and two bronze Lions for work for clients including IBM, Star Alliance and Microsoft.
This year, the agency was shortlisted for a record nine gongs and was the runner-up for the Cannes Lions Direct Agency of the Year honour.
Harrison is to be the first creative director to preside over the Direct jury. Last year, it was Fred Koblinger, the chief executive of BBDO Holdings and the managing director of Palla Koblinger Proximity.
Other former Lions Direct presidents include Howard Draft, the chairman of Draft Worldwide, and Daniel Morel, the chairman and chief executive of Wunderman Worldwide.
Harrison said: "In five years, these awards have become the benchmark for creative excellence in our industry."