Hugh Burkhardt, long time Professor of Mathematical Education and Director of Nottingham University’s internationally renowned Shell Centre, is an applied mathematician and strategic researcher-designer in education. Working in both the United Kingdom and the United States, he is particularly interested in the challenges of achieving change in school systems. Daniel Pead has been an IT leader of the Shell Centre team since spending his gap year working on the Investigations on Teaching with Microcomputers as an Aid project in 1983. He has worked on the Centre's contributions to reSolve, Bowland Maths, and World Class Tests, amongst others. He is particularly interested in the design of computer-based material for teaching and assessment – preferably both together! Kaye Stacey is an internationally renowned researcher, teacher educator, and a prolific designer of educational materials. She is Emeritus Professor Mathematics Education at the University of Melbourne and chaired the Expert Group for the 2012 PISA assessments of Mathematical Literacy. All three authors have received awards for contributions to educational design in STEM subjects from ISDDE, the International Society for Design and Development in Education.