Don't know if this adds much :-
From "Popular Music of the Olden Time" - William Chappell Vol 2, p641.

The subject of this ballad is mentioned in Evelyn's Diary, under the date of January, 1702-03. "News of Vice-Admiral Benbow's conflict with the French fleet in the West Indies, in which he gallantly behaved himself, and was wounded, and would have had extraordinary success, had not four of his men-of-war stood spectators without coming to his assistance; for this, two of their commanders were tried by a council of war and executed; a third was condemned to perpetual imprisonment, loss of pay, and incapacity to serve in future. The fourth died." Admiral Benbow was a thoroughly gallant seaman. He received his commission in the navy for his bravery in beating off a corsair, while in command of a merchant vessel. He was twice sent to the West Indies by King William. On the second occasion, he fell in with the French Admiral, Du Casse, in August 1702, near the Spanish coast. A skirmishing action continued for four days, but on the last the Admiral was left alone to engage the French, the other ships having fallen astern. Although thus single-handed, and having his leg shattered by a chain-shot, he would not suffer himself to be removed from the quarter-deck (in this respect the ballad is incorrect), but continued fighting until the following morning, when the French sheered off. The Admiral made signal for his ships to follow, but his orders received no attention, and he was obliged to return to Jamaica, where he caused the officers who behaved so basely to be tried. The report of the court-martial will be found in The Harleian Miscellany, vol. I, 1744. There was a treasonable conspiracy among the officers of his fleet, not to fight the French. Admiral Benbow did not survive this disappointment; it aggravated the effects of his wound, and he expired. The tune of Admiral Benbow is the vehicle of many country songs at the present time (1859), and used for Christmas carols. In the month of January last, Mr. Samuel Smith noted it down from the singing of some carollers in Marden near Hereford, to the words commencing,- "A virgin unspotted the prophets foretold."