One very late night or early morning in 1939, J.R.R. Tolkien awoke, a full story ready to burst from his already imaginatively feverish brain. Contrary to his normal hesitation and typical obsessive writing and rewriting, Tolkien’s short story, “Leaf by Niggle” emerged “virtually complete in my head. It took only a few hours to get down, and then copy out.”[1] If Tolkien had ever toyed with the ideas found in the novel—in terms of setting, character, or plot—he had no recollection of them or of any of it. Like Athena emerging whole out of the head of Zeus, “Leaf by Niggle” simply appeared on paper that very late evening or early morning in 1939, just prior to the beginning of the Second World War. Sometime in 1940, he read the story—presumably to an approving audience—to the Inklings. Again, the story just emerged, and Tolkien never even edited it after his initial copying it down. It was, he remembered fondly, “the only thing I have ever done which cost me absolutely no pains at all.”[2]
— Read on theimaginativeconservative.org/2019/11/leaf-by-niggle-jrr-tolkien-bradley-birzer.html