[2] Close kinsmen and powerful allies of the Plantagenet kings, especially Edward III, Richard II, Henry IV and Henry V, the Earls of Devon were treated with suspicion by the Tudors, perhaps unfairly, partly because William Courtenay, 1st Earl of Devon (1475–1511), had married Princess Catherine of York, a younger daughter of King Edward IV, bringing the Earls of Devon very close to the line of succession to the English throne.

During this period of dormancy, the de jure Earls of Devon, the Courtenays of Powderham, were created baronets and later viscounts.

[8] Baldwin de Redvers was a great noble in Devon and the Isle of Wight, where his seat was Carisbrooke Castle, and was one of the first to rebel against King Stephen (1135–1154).

He seized Exeter Castle, and mounted naval raids from Carisbrooke, but was driven out of England to Anjou, France, where he joined the Empress Matilda.

King John (1199–1216) forced her to marry Falkes de Breauté, but she was rescued at the fall of Bedford Castle in 1224 and divorced from him, as having been in no true marriage.

The fifth Earl's youngest daughter, Mary de Redvers, known as 'de Vernon', was eventually the sole heiress of the 1141 Earldom.

The Wars of the Roses continued and in 1470 the Lancastrian forces under Warwick prevailed, and Henry VI was restored to the throne.

When the Yorkists again prevailed in the following year, Edward IV had the legislation of Henry VI's second reign cancelled, and all of John Courtenay's honours were forfeited.

According to Cokayne, "on his death the representation of the ancient Earls of Devon (of the family of Reviers from whom the Courtenays had inherited it) and of the Barony of Courtenay (created by the writ of 1299) fell into abeyance between his sisters or their descendants, subject to the attainder of Edward IV (1461), which revived on that King's re-accession 14 April 1471".

[30] Sir Edward Courtenay (d.1509), great-nephew of the 3rd/11th Earl, fought on the winning side at Bosworth on 22 August 1485, ending the Wars of the Roses and two months later the new King, Henry VII (1485–1509), by letters patent dated 16 October 1485, created Edward Courtenay Earl of Devon (or Devonshire), with the usual remainder to the heirs male of his body.

William Courtenay (d.1511) had married Princess Catherine of York, a younger daughter of King Edward IV, and was thus brother-in-law to Elizabeth of York but nonetheless Elizabeth's husband Henry VII had Courtenay imprisoned and attainted for his supposed, but unproven, complicity in the conspiracy of Edmund de la Pole, 3rd Duke of Suffolk.

His lands were restored as far as was possible, and by letters patent of 10 May 1511, he was created Earl of Devon with remainder to the heirs of his body.

He died suddenly of pleurisy a month later on 11 June 1511, leaving his only surviving son, Henry Courtenay (d.1539), to inherit the earldom.

However, in 1538 he was tried, convicted, attainted and beheaded by the same king for conspiring with the Poles and Nevilles against the government of Thomas Cromwell in the aftermath of the Pilgrimage of Grace.

Were he to die unmarried, the viscountcy would become extinct, while the baronetcy would be inherited by his third cousin, another William Courtenay (1777–1859), who was Clerk Assistant to Parliament and High Steward of Oxford University.

William Courtenay (d.1859) persuaded the House of Lords that "heir male" in the last 1553 creation of the title had meant "heir male collateral", and that his cousin the 3rd Viscount was therefore also 9th Earl of Devon, and his ancestors the Courtenays of Powderham had been de jure Earls of Devon from 1556.

(A madman, John Nichols Thom, claimed to be "Sir William Courtenay" in 1832, and stood for Parliament twice, as representative of the extreme Philosophical Radicals, and proclaimed his right to the Earldom.

He organized an agricultural rising outside Canterbury in 1838, and was shot dead in the Battle of Bossenden Wood during its suppression.)

This is due in part to the differences between English and "law Latin", the language in which royal decrees were traditionally written.

[38] The heir apparent is the present holder's only son Jack Haydon Langer Courtenay, Lord Courtenay (born 2009) †: 1553 creation was with remainder to his heirs male whatsoever, so theoretically succeeded by his sixth cousin once removed; thus the 1831 revival was to the ninth member of the family with respect to said creation.