David Bell obtained his B.Sc. in Mathematics (1955) from the University of Manchester and his M.Sc, Ph.D. degrees (1962,1970) in Mathematics from the University of London. From 1955 to 1961 he worked as a research mathematician for the aircraft firm A. V. Roe and Co. Ltd., followed by a period as lecturer in Mathematics at the Bristol College of Science and Technology (1961-1964), and the University of Bath (1964-1967). His present joint appointment between the Department of Mathematics and the Control Systems Centre at UMIST was taken up as a lecturer in 1967 and senior lecturer in 1973.Peter Cook obtained his B.A. in Mathematics (1962) from the University of Cambridge and his Ph.D. (1966) in Theoretical Physics from the University of Manchester. He was then appointed lecturer in Applied Mathematics (1968) at the University of Kent. From 1971 to 1974 he was a Senior Research Fellow in the Department of Mathematics at the Loughborough University of Technology. Since 1974 he has been a lecturer in Control Engineering at the Control Systems Centre, UMIST.Neil Munro obtained his B.Sc. in Electrical Engineering (1962) from Strathclyde University and his M.Sc. (1967) and Ph.D. (1969) in Control Engineering from the University of Manchester. He was then appointed as a lecturer (1969), senior lecturer (1973) and Professor of Applied Control Engineering (1979) in the Control Systems Centre, UMIST. He has also spent some 10 years in industry as an electronics technician, development engineer and design engineer working for Barr and Stroud Ltd., Ferranti, Parkinson-Cowan Measurement and ICL.