"Oh who will plough the field now ... Since Johnny went a-thrashing the dirty King of Spain." Everyone, even the police, miss him. "His heavy loss we Bantry girls will never cease to mourn" if he dies "for Ireland's pride in the foreign land of Spain"
Sparling: "Taken from Graves' collection; on ballad-slips I have only seen very confused versions." The Graves reference is to Alfred Percival Graves _Songs of Irish Wit and Humour_ (London, 1884). I must be misreading this badly if it is an example of "Irish Wit and Humour." There are clever lines though, like the reference to the police: "The peelers must stand idle against their will and grain, For the valiant boy who gave them work now peels the King of Spain."
If the reference to "peelers" has always been part of "Bantry Girls" then it puts an earliest possible date on the ballad: Sir Robert Peel established the Royal Irish Constabulary in 1812 and its success led, in 1829, to the Metropolitan Police Act for London. Originally the term "Peeler" applied to the London constabulary. (source: _Sir Robert "Bobby" Peel (1788-1850)_ at Historic UK site.)
Here is a note from the MySongBook site Suzanne's Folksong--Notizen English Notes: "Learned from Tim Lyons of Clare. I mistook the locale for years and didn't realise that there was another Bantry, in North Co. Wexford, where this love song from the Peninsular War comes from. (Jimmy Crowley, notes 'Uncorked!')" Jimmy Crowley is the source for the site's text. The Peninsular War, 1808-1814, is against Napoleon's brother Joseph, installed as king of Spain. The Peninsular War reference fails my peelers reference suggestion.
This seems not to refer to Irish participation on the Cristino [supporting Queen Christina] side in the First Carlist War (1835-1837), which has the right date but wrong facts. - BS
The other possibility, I suppose, would be the War of the Spanish Succession (1701-1714); the British troops fought almost entirely in the Low Countries, but they were fighting against France, which was supporting the Spanish monarchy. This again fails the "Peeler" test, though.
Even more improbable are the various suggestions (repeated also in the Digital Tradition, e.g.) that this dates from the Peninsular Wars against Napoleon. The Peninsular War is not only is too early for the Peelers, but it also has its kings backwards: The British in the Peninsula were fighting against Napoleon, who had pushed aside the Spanish king (replacing him with Napoleon's brother Joseph, but no one except Napoleon would have called Joseph the King of Spain). - RBW