Still not clear what the 'British Hymn' refers to. Can't be 'God Save the King/Queen' as no-one knows its lyric, only the first verse. There are folk who were brownies or cubs in the 1970s or earlier who may know the third verse, but hardly anyone knows verse two (confound their politics, frustrate their knavish tricks", etc.). Possibly Leadbelly means Blake's Jerusalem? But neither are folk songs.

Me, I'd go for "The Rawtenstall Annual Fair" (which is a music hall song).

Or "The Lincolnshire Poacher".