Christie's has listed a letter in their upcoming Valuable Books and Manuscripts, London|9 December 2020 auction. £7,000-£10,000

J.R.R. Tolkien (1892-1973)
Letter to C. Gilmore. 3 July 1961
TOLKIEN, John Ronald Reuel (1892-1973). Typed letter signed ('J.R.R. Tolkien') to C. Gilmore Esq, Headington, Oxford, 3 July 1961.

One page, 255 x 202mm (pale toning, mild fading to signature). Envelope.

'I shall not write a sequel to The Lord of the Rings': a superb letter with important content, in which tolkien expounds his philosopy of storytelling. 'No story has any end. No picture has any boundary. But one has to put one's small vision into a frame, because you cannot see anything clearly unless you concentrate on it. I shall not write a sequel to The Lord of the Rings because, as is really clearly stated in the course of the story, it is the end of the kind of world about which I write: the twilight in which mythology and history are blended. After that there is only history'. Tolkien goes on to refer to the difficult and ongoing composition of The Silmarillion, 'a sequel (in the sense that it will be published after The Lord of the Rings), though the stories will be about the time before, in the First and Second Ages'.

Written between 1937 and 1949, The Lord of the Rings was published in 1954-55. By the time of his retirement from his academic positions at Oxford in 1959, the work's enormous success had already begun to make him a celebrity. The Silmarillion, although based on drafts which precede the composition of The Lord of the Rings, remained uncompleted on Tolkien's death, and was only published in 1977.

It was for sale as recently as March 2019 at Bonhams and sold for £4,800.