Henry Mainwaring had in 1610 obtained a commission from Lord High Admiral Nottingham to capture the notorious Newfoundland "arch-pirate" Peter Easton, feared to be hovering around the Bristol Channel.
This may have been just a convenient excuse for the well-armed Resistance, his small but speedy ship, to become a scourge to the Spanish.
On reaching the Straits of Gibraltar, Mainwaring had announced to his crew his intention of fighting the Spanish anywhere he found them.
He sails his fleet to Newfoundland in 1614, saying that the region is the best in which to recruit a pirate crew and reprovision his ships.
Mainwaring uses Easton's former headquarters at Harbour Grace as his pirate base and raids Spanish, Portuguese, and French ships.
In command of eight vessels off the coast of Newfoundland on June 4, 1614, Mainwaring plunders the cod-fishing fleet, stealing provisions and taking away with him carpenters and mariners.
In taking seamen, Mainwaring picks one out of every six.
In all, four hundred men join him willingly, while others are "perforstmen."
Born in Ightfield in Shropshire, Mainwaring is the second son of Sir George Mainwaring and his wife Ann, the daughter of Sir William More of Loseley Park in Surrey; his maternal grandfather is Sir William More, Vice-Admiral of Sussex; his brothers are Sir Arthur Mainwaring, Carver to Prince Henry, George Mainwaring, the defender of Tong Castle, and Sir Thomas Mainwaring, the Recorder of Reading.
The Mainwaring family is old and distinguished in England, probably having arrived in the train of William the Conqueror in 1066.
Mainwaring had graduated from Brasenose College at Oxford University, where he was awarded a B.A. in Law, at the age of fifteen, in 1602, then served as trial lawyer (admitted in 1604 as a student at Inner Temple), soldier (possibly in the Low Countries), sailor, and author (pupil of John Davies of Hereford) before turning to piracy.