Medley joins the agency in the newly created role this week and will work alongside agency founder Sara Pearson, who will continue in the role of agency chairman.
For the past three years, Medley has been MD at Publicis Consultants.
The new appointment comes as Pearson has been focused on building management consultancy business Cogn8 over the past to years, in partnership with Steven Esom, previously MD of Waitrose.
In his new role, Medley will run The SPA Way, as well as working to develop a broader 'media-focused' group offer that will be built alongside the core business.
Medley said of his move: 'The lure of independent agency life after a career in network groups is the kind of fresh challenge that smacks of perfect timing in light of Sara's business ambitions.'
Medley has also previously held senior director roles at GCI and Porter Novelli, during which time he advised clients including BP, BAA Retail and McDonald's.