It's an odd blend of documentary detail (the canal) and "Streams of Lovely Nancy"-esque extravagance (the castle and the ivy - although since ivy's evergreen, maybe that's based on fact too). Fascinating stuff - lovely tune, too.

Bob - you've got me thinking of counter-examples. There are songs in praise of heroes - Lord Franklin, Death of Nelson - and there are quite a few songs in the name of a hero, sung in the first person: Duke of Marlborough, Boney's Lamentation, and there's a variant of Valiant Sailor beginning "Lord Carter is my name". Those aren't usually local figures, though. Then there are all the convivial songs like Twankydillo, wishing "a health to" this or that person; they generally would be local. As a friend of mine sings,

Here's a health to the Secretary and also the Chair
And all party members, except Tony Blair

Entire songs in praise of a local worthy do seem to be a rarity, though.