Stewart is Sales Director for Telespazio in Germany. Graduating with a degree in Systems Engineering in 1992, Stewart trained and worked as a software engineer and ground systems architect until 2014, helping develop ground segment systems for many well-known space programmes, including: Rosetta comet chaser, Mars Express and Beagle 2, Galileo FOC, Meteosat Third Generation and OneWeb. From 2019 until 2024 he was Deputy Head of Strategy and Sales at Thales Alenia Space in the UK.