Surprised no-one's mentioned "The Great Plenipotentiary", said to have been composed by an eighteenth-century military man. Sample verse:

"The next to be tried was an alderman's bride
Whose cunt would have swallowed a turtle;
She had horn'd the dull brows of her worshipful spouse
Till they sprouted like Venus's myrtle;
But he rammed her so full she roar'd out like a bull,
And her cunt frothed like cream in a dairy
So tight was she stuck by that wonderful fuck
Of the great Plenipotentiary"

To the tune of "Sean Buidhe"