On Wilder Seas is inspired by a single line in a handwritten manuscript kept at the British Library in London. The author, an unknown sailor aboard the Golden Hind, reports Francis Drake’s exploits after he passed through Magellan’s Strait into the Pacific Ocean in September 1578.
Sailing up the coasts of Chile, Peru and New Spain, Drake attacked ports and ships as he went, including a Spanish merchant ship near Acajutla in what is now El Salvador.
According to the unknown writer: ‘Drake tooke out of this ship a pilate to cary him into the harbor of Guatulco, and also a proper negro wench called Maria, which was afterward gotten with child between the captain and his men pirates, & sett on a small Iland to take her adventures, as shalbe hereafter shewed.’ 
The date is not recorded – but from Spanish records we know this was April 4, 1579.
The manuscript does not mention Maria again until eight months later. On December 12, on the other side of the Pacific Ocean, Maria was abandoned on a barren, waterless island. Or as the writer puts it: ‘Drake left behinde him uppon this Iland… the negro wench Maria, shee being gotten with childe in the ship, and now being very great.’
Maria is named in only one other contemporary document: the deposition of John Drake at Santa Fe (now Argentina) in March 1584. John, who appears as a character in my book, was Francis Drake’s cousin and his page on the circumnavigation voyage. In 1582 he sailed for the Americas again, this time as captain of a ship in the fleet of Edward Fenton. The voyage was a disaster. After falling out with Fenton, who had decided to return to England, John Drake was attempting to continue the voyage to the East Indies when he was marooned and captured at the River Plate. When the Spaniards discovered his family connection, he was interrogated about the circumnavigation.
He told them: ‘They ran along the coast towards Guatulco, taking, on their way, a vessel bound for Lima in which there travelled a gentlemen named Don Francisco de Zarate…. [Drake] took from Don Francisco a negress named Maria and the pilot of said ship.’ 
When the first accounts of Drake’s voyage appeared in print: in 1589 in Richard Hakluyt’s Principall Navigations, in John Stow’s Annales published in 1601 and in The World Encompassed, published by Francis Drake’s nephew in 1628, Maria was not mentioned.
That is not to say she was unknown. Gossip, circulating since Drake’s return, told of the young African woman abandoned on a desert island in the East Indies.
In 1625, the first English translation of William Camden’s history of Queen Elizabeth’s reign was published. He refers to the ‘fair negresse’ taken by Drake, who later ‘inhumainly set that Negresse Maid on shore in an Island, after she was gotten with child in his ship.’ 
But perhaps the first reference to Maria appeared on the stage, not in print. On November 1, 1611 William Shakespeare’s new play The Tempest was first performed.
As Miranda Kaufmann reports in Black Tudors, the audience, at King James’s court would have heard the tale of Sycorax, a pregnant African woman, abandoned on a desert island by sailors. 
‘This blue eyed hag was hither brought with Child / And here was left by th’ sailers.’
A discourse of Sir Ffrances Drakes jiorney & exploytes after hee had past the straytes of Magellan into Mare del Sur & through the rest of his voyage afterward till hee arrived in England 1580 anno, British Library, Harley MS 280 ff 83-90. Also known as the Anonymous Narrative