At the Battle of Killiecrankie, 27 July 1689, 3,000 Highlanders, commanded by John Graham, Lord Dundeeathe aBonnie Dundeea of legendasupporting the cause of the deposed king James II (James VII of Scotland), swept down a Perthshire hillside and routed a professional army twice their size, commanded by General Mackay of Scourie, hurriedly raised in support of William of Orange. At the moment of victory, Dundee was hit by a single bullet and died shortly afterwards on the battlefield. Deprived of their charismatic leader, the Jacobite army fell to looting and squabbling and was defeated three months later at Dunkeld. According to a remarkable journal, transcribed by Ross Laidlaw, this fatal shot, which changed the course of history, was fired by Aprha Behn, the Jacobean poetess and playwright, who had been sent north as a spy by Williamas agents. She used an air gun, devised by Isaac Newton, which fired a silver bullet.