Sir John Colquhoun was appointed governor of the castle of Dumbarton, by King James I, for his fidelity to that king during his imprisonment in England. From his activity in punishing the depredations of the Highlanders, who often committed great outrages in the low country of Dumbartonshire, he rendered himself obnoxious to them, and a plot was formed for his destruction. He received a civil message from some of their chiefs, desiring a friendly conference, in order to accommodate all their differences. Suspecting no treachery, he went out to meet them but slightly attended, and was immediately attacked by a numerous body of Islanders, under two noted robber-chiefs, Lachlan Maclean and Murdoch Gibson, and slain in Inchmurren, on Loch Lommond, in 1439.