Now I've always known the Rule Britannia chorus as belonging to "My Father was the keeper of the Eddystone Light" - which is in the Digital Tradition, but without the chorus - which goes:

"Rule Britannia,Britannia Rule the Waves
- Britons never never never shall be -
marr-i-ed to a mer=ma-id,
at the bottom of the deep blue sea.

I think it was at Walton Foklk Festival a couple of years ago there were some foreign dancers (Romanian I think) who got very confused with this. When the chorus came, they recognised the Rule Britannia bit and joined in, and then got thriown bynthe last verse. "Is Patriotic song?" one whispered to me with a worried look. So I reassured him that it was.