Previously, Marshall worked in U.S. political campaigns for ten years.
Marshall has worked across a range of sectors, with particular experience in retail, consumer goods, energy, healthcare, and technology. He has also written and spoken extensively about digital and social media over the years. In 2014, Marshall authored Facebook Zero, a widely cited paper which evaluated the consequences of the decline in organic reach for branded Facebook communities. Since 2013, he has authored an annual trends review and forecast with his friend and co-author James Whatley.
Marshall has lived in London since 2008, and became a British citizen in 2015. He is an enthusiastic if not very gifted photographer, and is interested in history, politics, travel, and food.