Over the past 25 years Professor Evans has made a number of seminal contributions in the areas of signal processing, control systems and target tracking. He introduced the idea of the envelope-constrained filter, which has revolutionised the design of filters that must satisfy critical performance constraints. Envelope­ controlled filtering has now become a major area of study and is seeing wide application in communications and radar. He is also a leading international figure in adaptive control with input saturation constraints, target tracking in clutter and switched controller systems. He has publis