The poem was composed in 1818, written in the margin of a replica of Shakespeare's works, and published posthumously on November 8, 1838 in The Plymouth and Devenport Weekly Journal.
[1][2] In a letter from January 23, 1818, Keats writes, "I sat down yesterday to read King Lear once again; the thing appeared to demand the prologue of a sonnet".
for once again the fierce dispute, Betwixt damnation and impassion'd clay Must I burn through; once more humbly assay The bitter-sweet of this Shakespearian fruit.
and ye clouds of Albion, Begetters of our deep eternal theme, When through the old oak forest I am gone, Let me not wander in a barren dream, But when I am consumed in the fire, Give me new Phoenix wings to fly at my desire.
It is arguable that King Lear was the most significant Shakespearean play for Keats, and it inspired him to move on from Endymion to begin working on Hyperion, which he said would be written in "a more naked and Grecian manner".