  How protoplanetary discs evolve remains an unanswered question. Competing
theories of viscosity and magnetohydrodynamic disc winds have been put forward
as the drivers of angular momentum transport in protoplanetary discs. These two
models predict distinct differences in the disc mass, radius and accretion
rates over time, that could be used to distinguish them. However that
expectation is built on models that do not include another important process -
photoevaporation, both internally by the host star and externally by
neighbouring stars. In this work we produce numerical models of protoplanetary
discs including viscosity, magnetohydrodynamic disc winds, and internal and
external photoevaporation. We find that even weak levels of external
photoevaporation can significantly affect the evolution of protoplanetary
discs, influencing the observable features such as disc radii, that might
otherwise distinguish between viscous and wind driven discs. Including internal
photoevaporation further suppresses differences in evolution between viscous
and wind driven discs. This makes it much more difficult than previously
anticipated, to use observations of nearby star forming regions to determine
whether discs are viscous or wind driven. Interestingly we find that evolved
protoplanetary discs in intermediate FUV environments may be the best cases for
differentiating whether they evolve through viscosity or magnetohydrodynamic
disc winds. Ultimately this work demonstrates the importance of understanding
what are the key evolutionary processes and including as many of those as
possible when exploring the evolution of protoplanetary discs.
