This chapter sets out the taxonomy of non-statutory executive powers ultimately adopted. It is a very simple taxonomy that draws a fundamental distinction between statutory and non-statutory executive powers but no distinctions for the purposes of judicial review between non-statutory executive powers associated with the Royal Prerogative and those that are more mundane, and appear to be nothing more than the ‘residual liberties’ of the Crown as a legal person. Once the logic of office, official empowerment, and official action is adopted as a premise, the idea of the ‘third source’ as generally articulated simply falls away. While the distinction may be interesting or useful in a historical sense, it is of no relevance to the ‘how’ or ‘why’ of judicial review.