As The Plains of Abraham battle was eminent -- "when the first breathless messages from Vergor's post finally arrived with reports that the whole British army was established on the heights west of the town they were frankly disbelieved. ..... He had already sent an aide-de-camp to Vaudreuil's headquarters near the St. Charles bridge to ask what the Samos firing had been about. No answer had been received and Montcalm set off himself with his Scottish Jacobite aide-de-camp, the Chevalier Johnstone--he had fought with Prince Charles Edward at Culloden--to find out for himself." [POA]
The Chevalier Johnstone himself was an author of three volumes:
Volume III (The Campaign of 1760 In Canada) features an imaginary conversation between the two slain Generals (Montcalm and Wolfe) after the Battle of The Plains of Abraham:
Volume I is entitled "Memoirs of the rebellion in 1745 and 1746":
Another blog, "Flintlock and tomahawk," posted an excerpt of the Chevalier Johnstone's memoirs here.
For the story of the Jacobite who helped General Wolfe and the British in the same battle, see this blogpost. A short film featuring the painting of the Death of General Wolfe can be found here (also from the blog "Flintlock and tomahawk").