Thanks, Joe. The tune is definitely not related in any way to the one by Samuel Webbe. Here it is extracted, by software and manual post-editing:

X:1
T:Germany
I:linebreak $
M:2/4
L:1/8
Q:1/4=88
K:A octave=-1
a2e'c'| a2a2| d'bg2| g2ea| gabc'| a4| z2b2| c'bab| c'f'e'd'| % 14
c'bab| c'/d'/c'/a/b2-| b3c'/d'/| e'3f'/d'/| e'3f'/d'/| c'bag| a4|] % 21

Who knows it, and its origin? Original lyrics, perhaps anti-Napoleon? English or German?

I am not sure whether I got the ABC right, particularly whether the metric structure is really the original one. If someone knows better, please post a correction.

Happy Easter - or "what you celebrate" - to all!