I think I read a brief piece about this a long time ago -- as in, over twenty years ago. (Possibly in some sort of literary reference book.) As near as I can recall, the following sequence of events is supposed to have occurred in the real world, probably in the decade of the 1920s.
Some time after the end of World War I (then better known as "The Great War"), a group of poets in the United Kingdom contrived a hoax.
I believe that a bunch of them, well-acquainted, were all spending a weekend in someone's country house, and then someone suggested they invent the complete works of an imaginary poet whom they would allege had been one of the many brave young Englishmen whose lives had been cut short in the recent war.
Most of this fledgling poet's "complete works" were turned out within the next few days.
Then someone arranged to have it all published in one small volume, with one or more introductory pieces to "inform" the reader of when and where this talented youngster had been born, and had died in the war, and how one or more of his notebooks had been returned to his family, with his unpublished poetic efforts contained within. (This explained why nobody had ever heard of him before; he had never made a sale to any British periodical.)
I don't remember how long the hoax lasted, but eventually someone spilled the beans and admitted that it was pointless for critics to try to trace signs of the young poet's gradual psychological development, etc., in different poems written on similar themes, supposedly a few years apart, as he matured and reconsidered his previous attitudes on one thing or another.
A few months ago, I spent some time looking through Wikipedia pages on such subjects as literary forgery, nonexistent people used in hoaxes, etc., but I did not pick up the trail of this imaginary young poet. For some reason, it did not occur to me at that time to seek help on here.
Better late than never! Now that I've described what I am sure I once read, does anyone recognize this episode? If you remember the name of the fictitious poet, that probably will suffice to help me track down anything else I want to know about the hoax.