Affectionately nicknamed "Ugly James" by his descendants, James was one of the leaders of the Parliamentary Party in Guernsey in the 1640's; a merchant who imported and exported a wide variety of goods. 
"James de Havilland who was a partizan on the Cromwellian side during the Great Rebellion, and was one of the Parliamentary Commissioners appointed to govern the island of Guernsey. He, with Peter Carey and Peter de Beauvoir, were inveigled by Captain Bowden and made prisoners in the Castle Cornet on the 25th October 1643, whence they escaped at mid-day the 3rd of December following. ... James was sworn Jurat on the 1st November 1650, and at the Restoration was one of the Jurats who were continued in office by the King's order. He was subsequently deputed to Charles II., as Envoy to obtain a renewal of the island privileges. He died at Windsor whilst on that mission, and is buried in St. George's Chapel." 
(The name James is commonly written as "Jacques" in early records.)
Death & Burial
James died Oct 1674 in Windsor, England and is buried at St. George's Chapel.
Epitaph (translated from the Latin): "Here lies buried James de Havilland, Gent, of Guernsey, Justice to the Royal Court there, a man remarkable for his knowledge and piety, ambassador for his Country to King Charles II. After 62 years and 3 months, he won his reward of virtue, succumbing to death on 22nd day of October, A.D. 1674. His son, John de Havilland, placed this marble, sacred to the memory of his father."  Description of grave from a reference about the Monuments of St. George's Chapel of Windsor Castle: Black marble slab, 32 in. x 72 in., on which the arms are cut very deeply in a circle above the inscription. Ashmole (III, p. 179) and Pote (p. 379) state it lay in the South Aisle [of the Nave] which is the position shown in Emlyn's 1789 Plan. It was probably removed during the repaving of that year, and in the 1918 Plan is shown in its present position. (M.I. also given in Ashmole and Pote, loc. cit., and in Lansd. 939, f.53b. P.R., p. 200, where he is described as "a relat: of Dr. Saumares.)"
It may be possible to confirm family relationships with James by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree:
In order to mark a parent as 'confirmed with DNA,' you need to include the necessary DNA test matching information in child's the profile for at least two testers, including where the DNA tests were matched, the amount of shared DNA, and the estimated relationships. Also include the MRCA and how the testers relate to each other.
You can see what is required under the DNA Confirmation (click) topic of WikiTree's Help pages, as well as examples.