In his new role, Pattison will mentor the management team at Rezonence, a marketing technology company.
Pattison will remain the chairman of Gravity Road, which he joined in 2012, and the non-executive chairman of Newsworks. He left PHD in 2007, 17 years after launching the media agency.
Rezonence is working with Trinity Mirror to provide the publisher with its FreeWall, technology it says "lies between ad-funded free access models and closed paywalls to help effectively fund premium content".
The software asks the audience to engage with brand messages to access parts of a website.
Prash Naidu, the founding director and chief executive of Rezonence, said: "[David] will be a key asset to myself and the rest of the management team as we take the next steps in our fast-growing business."