Jersusalem

From the time I arrived in London until the time I left England I could get this song out of my head:

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.

When I saw green pastures or smoky factories I would begin to sing this annoying song. I thought it was a hymn. But googling it I find it was a poem by William Blake that was put to music. If you take it literally it seems to support the Glastonbury theory: that Jesus was brought up in England – that’s bizarre. But in it’s context it was more a socio-political statement about the dark side of the industrial revolution. (Wiki)

So why did we used to sing it growing up in church?
See some discussion. My favourite comment follows:

Countless school children have had to sing this as their"school song" and
many,many mourning families have included it in the funeral rites of a loved
one. It is even regarded as Britain's "unofficial national anthem" -
but what does it mean.? This is another example of us mouthing words we do
not understand just because we are too mentally lazy to find out.