The album this song, Jerusalem, comes from is Brain Salad Surgery by Emerson Lake and Palmer. The lyrics of the song are by poet, William Blake.
Of note for this continuing discussion of the book of Revelation is the line in the second verse, "I will not cease from mental fight, nor shall my sword sleep in my hand." The sword in the hand of a poet is his pen used to write words in this case for the purpose of ending injustice. Tomorrow, I will compare the sword guarding the Tree of Life in Genesis with the double-edged sword coming from the mouth of a figure in Revelation.
