In the summer of 1040, King Duncan I of Scotland went north from his power-base in the Scottish lowlands to deal with a troublesome relative, his cousin Mac Bethand mac Findlaich, the Lord of Moray. Mac Bethand, better known to English speakers as Macbeth (yes, THAT Macbeth), saw in Duncan an opportunity to bring more power to himself. King Duncan I was known as the “Sick” and was never particularly secure on his throne. Macbeth and Duncan met in battle near Elgin in the far north of Scotland. Here, on land well known to him and his men, Macbeth defeated his king and Duncan was killed on the field of battle. Macbeth would now be King of Scotland!
And, yes, William Shakespeare’s famous play about Duncan and Macbeth are based on these historical characters. The events of the play, however, do not adhere much to historical events.