David Doran graduated in 1950 with an external BSc (Eng). He then undertook National Service with the Royal Engineers in Malaya from 1953 to 1955. He is a Fellow of ICE and IStructE, a former member of Council of IStructE and Chairman of five Task Groups. From 1965 to 1985 he was Chief Engineer with George Wimpey plc, where he was Manager of the Civil & Structural Design Department with a staff of 300, and Head of QA for Wimpey Construction. Upon leaving Wimpey, David became an independent consultant and is retained by GBGeotechnics, Cambridge. He has been involved in several important publications since 1988. Bob Cather graduated in Materials Science from the University of Bath. He initially worked with The Marley Tile Co. Ltd. on product development and subsequently spent more than 30 years with Ove Arup & Partners. Bob has considerable expertise in the selection, design and performance of materials in the built environment. This expertise has enabled his specialist contribution to projects and for clients worldwide, covering all areas of construction.