Introduction: Revisiting knowledge in urban planning Planning has long been understood as a field ‘located precisely at the interface between knowledge and action’ (Friedmann and Hudson, 1974: 2). Exploring how knowledge gets translated into action has been ‘central to the concerns of planning theory’ (Campbell, 2012: 137), while plans themselves have been described as ‘a set of knowledge practices that physically construct a material reality’ (Tett and Wolfe, 1991: 199).