Richard Collier BSc, PhD, CEng, FIET began his research at Southampton University in 1963 and continued as a Research Fellow at the National Physical Laboratory until 1968, working on maser amplifiers. For the next three decades he was based in the Electronics Laboratory at the University of Kent where he both lectured and carried out research into various aspects of microwaves and guided wave theory, in particular the use of dielectric waveguides. He then spent six years at the Cavendish Laboratory at the University of Cambridge studying the microwave properties of thin films, and is currently a Praeceptor in Physics at Corpus Christi College. He has been a lecturer on the IET Microwave Measurements Training Course since 1983 and is the present chairman of its organising committee. A. Douglas Skinner MBE, CEng, MIET served in the Royal Air Force as an Air Radar Fitter from 1950 to 1967. On leaving the RAF he joined Marconi Instruments Ltd in the measurement standards laboratory and was Head of Laboratory from 1975 until his retirement in 1998. He is a member of the UK National Measurement System Advisory Council and serves as a member of the DTI NMS Electrical Measurements, Time, Frequency and Photonics Programme Committee, of which he was Chairman until 2002. Since 1998 Doug has worked as an independent consultant on the calibration of d.c., low frequency, radio frequency and microwave measuring instruments and measurement uncertainties. He is an active UKAS technical assessor and was awarded an MBE for Services to the Calibration Industry in 1990.