Fortescue’s family claims to have sprung from a follower of the Conqueror, but lived in comparative obscurity in south Devon between the 11th and 14th centuries. The judge’s father and namesake, himself a younger son, held lands said to be worth £20 a year in Combe, Efford and elsewhere in the parish of Holbeton, and made a name for himself as a soldier who fought at Agincourt and became captain of Meaux. He served two earls of Devon (Edward and Hugh Courtenay) as steward from about 1413 to 1422, was knighted by the duke of Bedford in about 1426, and died in or before 1435.
Although Fortescue had started to build up a practice in the central courts at Westminster and was admitted to Lincoln’s Inn before 1420, by the time of his earliest elections to Parliament for Tavistock he can hardly have established much of a reputation as a lawyer. Yet before his fourth Parliament (1425) he had become a governor of the Inn, and his opinion was evidently being treated with respect. In 1424 during a dispute between his younger brother, Richard, and the trustees of the estates of Thomas Stonor over the manor of Ermington, Stonor wrote to Sir John Fortescue instructing him to insist that Richard sealed the indentures ‘drafted be avyse and asent of yowre son Jon ... for yowre son Jonys honestie hanketh thereon’. Fortescue’s counsel was much in demand, and not only in his native shire. The city of Canterbury, for example, retained his services with a fee of £1 a year and a robe, from 1429 for at least ten years.
Fortescue was naturally consulted by the Lords in Parliament over such important matters as the impeachment of the marquessof Suffolk in 1450, and Speaker Thorpe’s case in 1454; and he was asked by several members of the Upper House to act as a trustee of their estates, or to settle disputes over inheritance. Accordingly, he appeared as an arbitrator in such debates as the disposition of the Fastolf and Berkeley estates, and he served as either a feoffee-to-uses or executor for the Lords Cromwell, Fanhope, Cobham and Bonville, Elizabeth, Lady Ferrers of Chartley, Thomas, earl of Devon, Archbishop Chichele, Cardinal Kemp and even Richard, duke of York.
Fortescue spent the following two years in Scotland, acting as ‘chancellor’ and councillor to Henry VI, and it was probably there that he wrote De Natura Legis Naturae and other tracts on the question of the royal succession. In March (?) 1462 Henry gave him letters of credence to Louis XI of France, his mission being to ask support for the exiled Lancastrians. He crossed from Scotland to Sluys with Queen Margaret in July 1463, and they eventually settled at the castle of Koeur in St. Mighel, where they lived in extreme poverty. Fortescue spared no effort to procure assistance from the kings of France and Portugal in order to bring about Henry VI’s restoration and, calling himself ‘Chancellor of England’, he wrote several memoranda on the subject for Louis XI’s attention. During the years of exile he devoted himself to the education of Edward, prince of Wales, and composed De Laudibus Legurn Anglie and The Governance of England. He was a leading negotiator in the talks conducted at Angers in 1470 between King Louis and the earl of Warwick, thus promoting the momentous alliance between the earl and the queen; and on 14 Apr. 1471, after Henry VI’s readeption, he sailed for England with Queen Margaret and Prince Edward. Proclaimed a traitor by Edward IV a week later, he was captured at Tewkesbury on 4 May. Fortescue’s fidelity to the Lancastrian cause was unshaken so long as Henry VI and his son were alive, but after their deaths he sought a general pardon from Edward IV and even offered him his services as a councillor. Nevertheless, it was not until October 1473, after he had written a Declaracion upon certayn wrytinges, refuting his earlier arguments about the royal succession, that he was permitted to present a petition to Parliament for the reversal of his attainder and the restoration of his estates.