In 1335, forty-one years after the death of his second cousin once-removed Isabel de Redvers, suo jure 8th Countess of Devon (died 1293) he was officially declared Earl of Devon, although whether as a new creation or in succession to her is unknown, thus alternative ordinal numbers exist for this Courtenay earldom.

[4][5] With his father, he also rebuilt Okehampton Castle, expanding its facilities and accommodation to form a hunting lodge, retreat[6][7] and luxurious residence.

Courtenay joined King Edward I at the long siege of Caerlaverock Castle, just over the Solway Firth, for a fortnight in July 1300.

Courtenay may have been with the English King when he sat down in Sweetheart Abbey to receive Robert Winchelsey, Archbishop of Canterbury, who had travelled north with a demanding missive from Pope Boniface to cease hostilities.

The agenda included redrafting the Royal Forest Charter, which had no precedent since it was first introduced in the reign of Henry II, 150 years earlier.

But the King needed money and was required by Parliament to surrender his absolute authority and ownership of what became community forests.

In 1306, the Prince of Wales was despatched into Scotland; the vanguard was led by Aymer de Valence, the King's half-uncle.

On 19 June, Valence, who had cut a swathe through the Lowlands, fell on the Scots army at Methven in the early dawn.

Struggling into the saddle towards the Solway Firth, King Edward died at Burgh by Sands, awaiting a crossing.

As a veteran campaigner, he later aimed to ingratiate himself with young King Edward III, and so refused the Third Penny from the Exchequer.

By his wife he had five sons and two daughters: Courtenay died at Tiverton Castle on 23 December 1340, and was buried at Cowick Priory, near Exeter, on 5 February 1341.