Dewi is the Chief Software Engineer at Callen-Lenz Associates Ltd. He is also a director at Software Safety Limited and Aeronautique Associates Ltd. He is a chartered engineer with over 35 years’ experience of high integrity software development. He has worked on a number of civil and military aircraft programmes, including Airbus A380 and Boeing 787. He was one of the developers of the SPARK Examiner and a member of the committee that wrote DO-178C.