The following two paragraphs are a barely–edited version of the introduction to the relevant Wikipedia page:
Kubla Khan; or, A Vision in a Dream: A Fragment" is a poem written by Samuel Taylor Coleridge, completed in 1797 and published in 1816. According to Coleridge's Preface to Kubla Khan, the poem was composed one night after he experienced an opium–influenced dream. The previous evening he'd read a work describing Xanadu, the summer palace of Kublai Khan, the Mongol ruler and Emperor of China. Upon waking, Coleridge set about writing the lines of poetry that came to him from the dream, until he was interrupted by "a person on business from Porlock". He was unable to complete the poem according to his original 200–300 line plan, as the interruption had caused him to forget the lines. He left it unpublished, and kept it for private readings for his friends until 1816 when, at the prompting of Lord Byron, it was published.
Some of Coleridge's contemporaries denounced the poem, and questioned his story of its origin. It wasn't until years later that critics began to admire the poem openly. Most modern critics view Kubla Khan as one of Coleridge's three great poems, along with The Rime of the Ancient Mariner and Christabel. The poem is considered one of the most famous examples of Romanticism in English poetry. A copy of the manuscript is a permanent exhibit at the British Museum in London.
Porlock is a small coastal town in west Somerset. Coleridge was living at the time in Nether Stowey, which is a few miles west of Bridgwater and about 20 miles from Porlock.
The actual identity of the person from Porlock remains a mystery, and probably always will. Some – including Stevie Smith, in one of her own poems – have suggested that Coleridge invented him (or her), to explain his inability to complete Kubla Khan.
© Haydn Thompson 2016