UHECR sources and transport
In this review, I will reflect on the lessons learnt in the past decade with regards UHECR propagation and their secondary signatures. Starting from a consideration of their travel through extragalactic space, consideration will be made about what can be said about their source evolution. Complimentary to this discussion about the propagation of the UHECR primaries, the information conveyed by their secondary gamma-ray signatures will also be addressed. Building on the need to satisfy the multiple constraints from these different messengers, the landscape of solutions to this problem are considered, noting in particular the attractive features provided by sources which possess a negative evolution with redshift. Examples sources which possess such an evolution are discussed, along with the further challenges such a scenario faces in lights of recent improvements made in our understanding of the diffuse gamma-ray background.