A nobleman by birth, he left England after the House of Commons sided with his stepmother in a legal dispute over his inheritance, and became a mercenary in Morocco and later a Barbary corsair.

Verney was among the most successful captains to operate on the Barbary coast during the early 17th century and, despite having no seafaring experience, was one of four leaders of the Tunisian pirate fleet commanded by John Ward.

Though little of his childhood is recorded, according to the Dictionary of National Biography, he had "all the advantages that a fine face and figure, great personal courage, and a magnificent taste in dress could bestow".

Crewe's pleading to the House on behalf of the Sir Edmund's widow as well as testimony of several surviving committee members of the 1597 Bill damaged Francis' case.

[3][4][8][9] Family tradition claims he went to Morocco where he joined Captain John and Philip Giffard, both relatives of the Verneys, who commanded an army of two hundred fellow Englishmen,[6] mostly gentlemen volunteers, in the service of Muley Sidan, a claimant to the Moroccan throne.

[1][3] King James grew so concerned over Verney's activities that he assigned a ship-of-war to escort merchant vessels en route for Aleppo in the Levant area.

[4] During this period, Verney was one of the four leaders in the Tunisian fleet headed by John Ward,[4][11] Richard Bishop, and Kara Osman,[12] the latter captain of the Janissaries at Tunis.

[13] In December 1610, according to claims made by the Venetian ambassador in Tunis, he and Ward were accused of "turning Turk" by becoming converts to Islam[8] causing a sensation in royal society when news reached back to England.

[4][9] This was a charge often made against corsairs of European origin as many, Verney included, often adopted the clothing worn by locals after settling in Algiers or Tunis.

English merchant John Watchin later obtained a formal certificate of his death, signed by Don Peter Garcia, which he forwarded with Verney's personal effects to Claydon House.

[2][3][4][9] Though common among the Barbary corsairs, as Muslim rulers sanctioned attacks on Christian merchants "as part of a larger jihad against the infidel", Francis Verney's conversion to Islam caused considerable controversy in his native England.

[17] Of the personal effects sent to the Verney family by John Watchin, which included a turban, slippers, silk tunics, and pilgrim's staff, Lady Frances made mention that all were still preserved at Claydon House.

The title character of the 1940 swashbuckler film The Sea Hawk, played by Errol Flynn, was inspired by the lives of both Verney and Sir Henry Mainwaring.