Orua, here's my interpretation. It's not authoritative at all, so play at your own risk! He does it in F, so I'll give you those chords, though I play it in a different key. Hope I can get the formatting right. . .

F Bf F C Bf F
When Boney commanded his armies to stand
Bf F Dm C Bf
He levelled his cannon right over the land
F Bf F C Bf F
He levelled his cannon his victory to gain
Bf F Dm C Bf
And he slew my light horseman on the way coming home

The chorus is the same as the first two lines of the verse. If you're like me and don't care for playing loads of Fs and B flats, but still want to play it in F, you could always capo up to the third fret and substitute D for F, G for Bf, A for C, and Bm for Dm.

Or let me know if you'd like it in another key and I might be able to help.

All the best, Margaret