At the heart of the collection is S. Lester's "diary" written between 1935 and 1946 when he served with or for the League of Nations, in Geneva and Danzig. S. Lester kept a considerable number of letters and texts of all kinds during his life. His notes were inspired by minor and major events, the working of the League of Nations, personalities he met, political developments, some family matters, and fishing. They varied in length between a half page and five pages or more, at times on a daily or twice daily basis, followed by periods when nothing was put down. A large part of the journal (1935-1941) was hand-written in note-books, the rest was typed on loose-leafs by S. Lester himself or his secretary, with date and place and often annotated "private", or "secret", or "confidential".
After his death in 1959, and several moves, all of these papers were mislaid and presumed to be lost. However, in 1980 an important part of his journal was found covering much of 1935-1941. These papers were thought to be all that had survived, and were, therefore, copied, bound under the title "Diary" together with some less interesting papers. Subsequently three more batches of papers turned up including the rest of his journal for 1934-1946, and all his other papers from 1929 to 1959.