The Willgerodt reaction[cite]10.1002/cber.18870200278[/cite], discovered in 1887 and shown below, represents a transformation with a once famously obscure mechanism. A major step in the elucidation of that mechanism came[cite]10.1021/ja01157a034[/cite] using the then new technique of 14C radio-labelling, shortly after the atom bomb projects during WWII made 14CO2 readily available to researchers. Here I am going to start the process of applying the far more recent technique of quantitative quantum mechanical modelling to see if some of the proposed mechanisms stand up to its scrutiny.