In common with many Australian organic chemists of my generation, as a graduate student I was trained in the general area of natural products chemistry. In the mid-1960s I continued this work at Cambridge (UK), working with A. R. Todd on aphid pigments. Dudley Williams arrived from Stanford during this period, and my collaboration with him in those early days introduced me to the mysteries and delights of a technique and a topic completely new to me: applied mass spectrometry and the fundamental reactivity of positive ions in the gas phase. Dudley's drive, enthusiasm and scientific curiousity have always been an inspiration to his students and colleagues, and it is therefore of no surprise that after my appointment to Adelaide my students and I continued work in the area of positive-ion mass spectrometry with particular emphasis on rearrangement reactions. Apart from a joint project (with Peter Derrick) on the application of isotope effects on the McLafferty and allied rearrangements,'*' and my recent and arguably belated return to natural product chemistry with our recent structure determination of a variety of amphibian peptides using fast atom bombardment mass spectrometry (FABMS) and other techn i q u e ~, ~ our work on positive ions terminated in the late 1960s. But this was the catalyst to all of our subsequent work in gas-phase ion chemistry during the next 25 years.