From 1 January 1915 to 29 July 1916, Francis Puryer White (1893-1969), a third-year Cambridge mathematics student, kept a detailed diary.  In it he chronicled his academic, spiritual, and recreational life as he passed from undergraduate to postgraduate under the cloud of the First World War.  In my talk I shall describe some of the contents of White’s diary, prefaced by a few remarks about diaries as sources in history of mathematics.