Dr McFadden is the recognised world authority on the analysis and interpretation of geomagnetic reversal chronologies. Using highly innovative analytical methods his work completely changed our understanding of the process by which the geomagnetic field changes polarity. He is at the forefront of modern geomagnetism providing the important link between palaeomagnetism and dynamo theories. He has developed specialised statistical techniques that provide the standard tests for analysing palaeomagnetic data. He was the first to recognise that the differential acquisition of thermoremanent magnetization in host rocks could be used to estimate emplacement temperatures, showing that kimberlites were emplaced at surprisingly low temperatures.