The poem was inspired by the old legend that Jesus, whilst still a young man, accompanied Joseph of Arimathea to Glastonbury via the nearby Roman port. Blake's biographers tell us that he believed in this legend.
And did those feet in ancient time Walk upon England's mountains green? And was the holy Lamb of God On England's pleasant pastures seen?
And did the Countenance Divine[?] Shine forth upon our clouded hills? And was Jerusalem builded here Among these dark Satanic mills?
Bring me my bow of burning gold: Bring me my arrows of desire: Bring me my spear: O clouds unfold! Bring me my chariot of fire.
I will not cease from mental fight, Nor shall my sword sleep in my hand Till we have built Jerusalem In England's green and pleasant land.