Grainger is leaving after ten years as CEO and 26 years at the company in total. He plans to pursue new opportunities in the burgeoning content marketing sector.
Cremer joined Redwood in 2008 with 20 years' experience as a journalist and editor in consumer magazines and branded content. A judge for the Cannes Lions Branded Content and Entertainment category in 2012, she is widely respected in the content marketing industry for her digital capability, energy and results-oriented approach.
During Grainger's term as CEO he led Redwood's transition from a print-based contract publisher to a provider of multi-channel content strategy and solutions for clients including Barclays, Boots, Marks & Spencer, Volvo, Land Rover and Virgin Media.
Cremer said: "I'm excited to be taking the reins at such an important time. I have a great team around me, terrific clients to work with and huge ambition for our business."
Cilla Snowball, AMV Group CEO, said: "Redwood is a great business and we're grateful to Keith. Sad as we are to see him move on, Sara is waiting in the wings and ready to lead the business forward to the next stage of Redwood's development."