Martin Sorrell leveraging his experience for S4 to own the Digital Marketing Space Founder of WPP plc Sir Martin Sorrell, the British multinational advertising and public relations company, effectively the largest marketing company in the world, jumped ship April last year to form S4 Capital which has posted pre-tax operating profits of $20.1m from revenues of pro forma revenues of £135.9m. “The company’s purely digital model based on first-party data fuelling digital content and programmatic…