"Usher’s book has left few bibliographic stones unturned. The scope of the research is amazing... Usher, the editors of Global Pentecostal and Charismatic Studies, and Brill are to be thanked for producing what will long be a crucial standard work for the study of UK Pentecostalism, Pentecostal mission, and more generally of global Pentecostalism." - David Bundy, Manchester, UK, in: Journal of the European Pentecostal Theological Association (2022).“It is extremely rare to find, among those who have written on early Pentecostal figures, many who have taken the time to work in such detail and it may be the first such study that I have found on a British figure. It is first rate.” – Cecil M. Robeck, Jr., Professor Church History and Ecumenics, Fuller Seminary.“Undoubtedly highly original and a significant contribution to knowledge…some truly excellent archival research underpinning the writing….” – Andrew Davies, University of Birmingham.