he fiction Tolkien sought to maintain was that LotR (and the Hobbit and the Silm) were actually ancient
manuscripts (written by Frodo and Bilbo, respectively) of which he was
merely the editor and translator (a situation identical to much of his
scholarly work). He never stated this directly but it is implicit in
the way in which many sections of LotR outside the story are written.
Thus, the Prologue is plainly written as though by a modern editor
describing an ancient time. Other examples are the introductory note
to the revised edition of the Hobbit, the Preface to
The Adventures of Tom Bombadil, and parts of the Appendices, especially the introductory note to Appendix A, Appendix D, and Appendix F. Most interesting of all is the Note on the Shire Records, where Tolkien further
simulates a real situation by inventing a manuscript tradition (the
suggestion was that Frodo's original manuscript didn't survive but
that a series of copies had been made, one of which had come into
Tolkien's hands).This entire notion was by no means a new idea: many authors have pretended that their fantasies were "true" stories of some ancient time. Few, however, have done so as thoroughly and successfully as did Tolkien. The most effective component of his pretence was the linguistic aspects of Middle-earth, for he was uniquely qualified to pose as the "translator" of the manuscripts.