Bilbo´s treachery

[Zigûr]

Originally Posted by Pitchwife

To the best of my knowledge, A & U didn't see anything of the First Age materials until after The Hobbit had been published and become a success and the question of a sequel came up, and then rejected it as unsuitable for the audience of TH - which is a good thing, for we wouldn't have The Lord of the Rings otherwise.

Yes, I believe Professor Tolkien offered The Silmarillion to Allen & Unwin after the success of The Hobbit, not before, when they requested more fiction from him, but they wanted more about Hobbits.

Of course, the narratives which contributed to The Silmarillion, including 'The Fall of Gondolin', were under composition in late 1916/early 1917 and continued over subsequent years. They were not merely a series of 'notes' but rather fleshed-out (if in some cases unfinished) narratives. This is, of course, all detailed in the two volumes of "The Book of Lost Tales" published as the first two volumes of "The History of Middle-earth".