Mowlem began his career in single seaters racing up to Formula 3 level and got his big break when he was chosen personally by triple Formula One World Champion Jackie Stewart to join his "staircase of "talent" team in the junior single seater formula, alongside drivers of the calibre of Dario Franchitti, Allan McNish and Gil de Ferran. He switched to sportscars in 1996, winning the Class 1 championship of the British Porsche Cup and then gained international recognition the following year when he won all 17 races of the British Porsche Cup to become British champion. This launched his professional career in World Sportscars. Later in his career he gained further international attention for his work as a driver of the hybrid-powered Ginetta Zytek prototype racer in the ALMS in 2008 and 2009. In 2010, Mowlem was a Lotus Racing factory driver, driving the American Le Mans Series (ALMS) and in the International GT Open Series for sports cars in Europe. His latest driving championship came in the European Le Mans Series in 2013. Mowlem raced in the ALMS series every year that sanctioning body held races. Mowlem also operates his own driving academy, working with both corporate clients and drivers wishing for a career in racing.