Hornby recently announced he had been appointed as chairman of sports-focused talent company Hiro, ahead of the Rugby World Cup.
The agency stated Hornby was originally hired to support the board in delivering its five-year mission, which has been completed. This consisted of tripling the business in size to bring in a turnover of £11m this year, setting up a London office in 2014 and acquiring Pumphouse Productions in February 2015.
Rick Stainton, Smyle's managing director, said: "David has played a significant role in helping the board through our growth mission, the recessionary impact and a focus on growing up internally. The company now has different requirements of support for its next development phase and David also has multiple other new projects he needs to focus on."
Stainton added that Hornby would remain a shareholder in the business.
Hornby added: "It has been a real privilege to work with such an amazing team over the last five years. We developed a strong and clear vision for Smyle. Our team, partners and customers have helped us achieve this great success together.
"But as with all things, there comes a time to move on. The events and live communications industry is changing rapidly and I look forward to the next opportunity and wish Smyle continued great success in the years to come."
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