From The Scot's Peerage
1:
Mary, Countess of Menteith, succeeded her uncle Sir Murdach, who is said to have held the earldom by her consent. In April 1320 Sir John Menteith, her grand uncle, is designed guardian of the earldom of Menteith, even though Murdach was nominally Earl, and it may be he thus safeguarded the interests of the heiress. The date of her birth is not known, but it must have been before 1306.
Before May 1334 she had married Sir John Graham, and it was probably then or at an earlier period that she received from Earl Murdach a grant of the lands of Aberfoyle, Buchlyvie, Boquhapple, and others, forming a considerable portion of the earldom.
After that date Sir John is found bearing the title of Earl of Menteith. As such he is witness to a charter of uncertain date, by Robert the Steward of Scotland to William Douglas of Bondingston and other lands in the barony of Dalkeith. As Sir John of Graham, Earl of Menteith, he was one of the jury who, on 7 June 1344, the Earl of Fife being foreman, found Malise, Earl of Strathearn and Caithness, guilty of treason for surrendering his earldom of Strathearn into Edward Baliol's hands.
Two years later the Earl of Menteith came to an untimely end. He had accompanied King David ii. on his fateful expedition to England in 1346, and was present at the battle of Neville's Cross on 17 October. There he fought with great bravery in a futile attempt to change the fortune of the day, and was taken prisoner. Later he was conveyed to the Tower of London, on 22 February 1346-47 was condemned to be executed as a traitor, a sentence which was carried out a few days later, on or before 6 March.
The Countess of Menteith survived her husband for some years, and granted various charters, chiefly in favour of the Campbells, who were allied to her by marriage. It is not exactly known when she died, but there is ground for believing her death to have taken place before April 1360, when a papal dispensation styles her daughter Countess of Menteith.
Footnotes
[1] The Scot's Peerage, Ed. James Balfour Paul, Vol 6, 1906, pages 137-138