One of the great documents of the 20th century is the founding deed of the Joseph Rowntree Reform Trust, which directs enormous donations into seeking out the underlying causes of weakness and evil, sacrificing charitable status and tax breaks to allow the financing of those seeking political change. An exemplar of its aims was Benjamin Seebohm Rowntree, third son of the mighty Joseph who wrote the deed. His pioneering work on poverty broke the comforting nostrum that the poor were responsible for their own plight. Low wages were shown unquestionably in Seebohm's work to be the underlying cause, but he was not content just to prove this. He followed his father's wishes in taking remedial action, using not only his intelligence and wealth but an admirable enthusiasm for going on the stump. He knew the poor intimately through years of voluntary teaching at York Quakers' adult school and a new accession to his archive at York University shows how well he put his case. Through his family's generosity and the enthusiasm of Frank Field, who carried the same torch in the Low Pay Unit and Child Poverty Action Group, Seebohm's travelling slide lecture is now safely in the Borthwick Institute. Drawing on marketing techniques from Rowntree's chocolate company, it shows how campaigning against poverty can be as satisfying as eating a Kit Kat. The devil's hold on fun is not as unchallenged by the virtuous as we are sometimes inclined to think.