Butterfield apparently maintained his papers in rough order during his life. At the commencement of the compilation of this catalogue, the papers were found to be grouped in a succession of folders and box files, most of which had been allotted brief titles by Butterfield. During the process of arrangement and listing, the papers were sorted into files based on Butterfield's own system. The integrity of the contents of each of Butterfield's files has on the whole been respected; only in a few cases have papers been transferred from one file to another in order that related correspondence or other material may be located together. In most cases, the titles of the files in this list are Butterfield's own; only when a title was potentially misleading to researchers, or bore no relation at all to the contents of the file, was it altered. There was no order apparent in the sequence of files as they were found; the present arrangement has adopted a series of broadly thematic sequences. Within each file there has frequently been some re-ordering of papers: in particular, runs of correspondence have generally been arranged in chronological order. A large portion of Butterfield's correspondence was found partially arranged in alphabetical order, and this material was sorted and listed by Dr Mark Nicholls before the present catalogue was undertaken. The resulting list, with a few minor emendations, now comprises the final file entry of this catalogue, 531.