Protoplanetary discs: the role of theory in a data rich era

The last decade has witnessed unprecedented advances in the observational characterisation of protoplanetary discs and their nascent planetary systems, thanks in large part to the transformative capabilities of ALMA (the Atacama Large Millimetre Array). In the first part of my talk I will describe how the relatively simple physics governing the dynamical evolution of drag coupled dust grains plays a crucial role in interpreting disc imaging data and will describe progress in `weighing' planets in discs, measuring their migration and assesssing the role of chemical transport on grains in driving the ambient chemistry in planet forming regions. In the last part of the talk I will instead describe a situation where theory currently outstrips observations, considering the role of ultraviolet radiation from the star fprming environment in photoevaporating protoplanetary discs. I will discuss the prospects for assessing the viability of planet formation in the diverse environments experienced across cosmic time.