From what I can gather, Blake might also be referring to the legend that Jesus may have visited England when he was a young bloke. Check out
this site for more info. Here's a bit of cutting and pasting for yis:
There are at least four separate and independent British traditions that say that Jesus as a youth travelled to Britain with his uncle Joseph of Arimathea, spending many years in Glastonbury, which was a prominant center of Druidism. This is also confirmed by many independent sufi traditions which link sufism and Druidism. (See The Sufis, Indries Shah.)
Some interesting stuff there, actually.
Anyway, here's Blake's poem. It's sort of disappointing in a way, because I don't know exactly how much of the great lyrics on "The Chemical Wedding" were written by Bruce and how much was lifted from Blake's poetry.
And did those feet in ancient time
Walk upon Englands mountains green?
And was the Holy Lamb of God
On Englands 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 Englands green and pleasant land.