William Bonfield is Emeritus Professor of Medical Materials at the University of Cambridge. His first research at Honeywell was on microplasticity in polycrystalline materials with direct applications to space vehicles. His interest in biomaterials started simultaneously, when he applied his microstrain measuring technique to ivory and cortical bone. He pioneered hydroxyapatite-reinforced polyethylene, which matches the deformation characteristics of bone. It stimulates natural reinforcement, and the hydroxapatite in a polymer matrix gives superior fracture resistance. This has been applied in middle ear implants and 22 different prostheses. Currently he is developing other biomaterials for maxillo-facial reconstruction, spinal implants, and joint prostheses. In 1998 he was appointed CBE.