I'm surprised no one's mentioned it, but I first encountered this song as a refrain in a Monty Python's Flying Circus skit. Unfortunately, I can't remember any other details of the skit at the moment.

Since that formative moment (probably in my early teens), I've married into an English family. My mother-in-law knows the song by heart I think, and I heard it on Songs of Praise during a recent visit to Britain (my tastes run more to Airport or Eastenders, but my wife's granny you know...)

I'm not usually the hymm sort, but I love the song. I originally got the imperialist interpretation, too, but now I'm leaning more toward the socialist. In fact, I happened upon this list when I did a web search for the lyrics after reading a Marxist-POV article quoting Blake. It doesn't mention that it became a hymm, but it does discuss the poem from a socialist perspective. See David Harvey, "Labor, Capital, and Class Struggle Around the Built Environment in Advanced Capitalist Countries," p. 27 in Kevin Cox, ed., Urbanization and Conflict in Market Societies, Chicago: Maaroufa Press, 1978.

Sorry I'm so wordy ...

Christian