No one knows precisely where Cooleridge was interrupted. The site marks the town where Cooleridge wrote Kubla Kahn but within the town the poem was probably written at Culbone Parsonage or Ash Farm.
The Person from Porlock was an unwelcome visitor to Samuel Taylor Coleridge during his composition of the poem Kubla Khan. Coleridge claimed to have perceived the entire course of the poem in a dream (possibly an opium-induced haze), but was interrupted by this visitor from Porlock (a village in the South West of England, near Exmoor) while in the process of writing it. Kubla Khan, only 54 lines long, was never completed. Thus "Person from Porlock", "Man from Porlock", or just "Porlock" are literary allusions to unwanted intruders who disrupt inspired creativity.