His 17-year reign was mostly peaceful, although in 1054 he was faced with an English invasion, led by Siward, Earl of Northumbria, on behalf of Edward the Confessor.

The name Mac Bethad (or, in modern Gaelic, MacBheatha), from which the anglicized "MacBeth" is derived, means "son of life".

[4] Some sources make Macbeth a grandson of King Malcolm II, presumably through his daughter Donada, and thus a cousin to Duncan I, whom he succeeded.

[7] Whatever the true state of affairs in the early 1030s, it seems more probable that Macbeth was subject to the king of Alba, Malcolm II, who died at Glamis, on 25 November 1034.

The Prophecy of Berchán, apparently alone in near-contemporary sources, says that Malcolm died a violent death: calling it a "kinslaying" without actually naming his killers.

[8] Tigernach's chronicle says only: Máel Coluim son of Cináed, king of Alba, the honour of western Europe, died.

Duncan appears to have been tánaise ríg, the king in waiting, so that, far from being an abandonment of tanistry, as has sometimes been argued, his kingship was a vindication of the practice.

[12] There he was killed in action, at the battle of Bothnagowan, now Pitgaveny, near Elgin, by the men of Moray led by Macbeth, probably on 14 August 1040.

The most common assumption is that Karl Hundason was an insulting byname (Old Norse for "Churl, son of a Dog") given to Macbeth by his enemies.

[20] According to the Orkneyinga Saga, in the war which followed, Thorfinn defeated Karl in a sea-battle off Deerness at the east end of the Orkney Mainland.

Finally, a great battle at Tarbat Ness[21] on the south side of the Dornoch Firth ended with Karl defeated and fugitive or dead.

The campaign led to a bloody battle at Dunsinane,[24] in which the Annals of Ulster reported 3,000 Scots and 1,500 English dead, which can be taken as meaning very many on both sides.

Macbeth did not survive the English invasion for long, for he was defeated and mortally wounded or killed by the future Malcolm III ("King Malcolm Ceann-mor", son of Duncan I)[26] on the north side of the Mounth in 1057, after retreating with his men over the Cairnamounth Pass to take his last stand at the battle at Lumphanan.

The Duan Albanach, which survives in a form dating to the reign of Malcolm III, calls him "Mac Bethad the renowned".

[30]Macbeth's life, like that of King Duncan I, had progressed far towards legend by the end of the 14th century, when John of Fordun and Andrew of Wyntoun wrote their histories.

In Shakespeare's play, which is based mainly upon Raphael Holinshed's account and probably first performed in 1606, Macbeth is initially a valiant and loyal general to the elderly King Duncan.

Historian Peter Berresford Ellis suggested that Shakespeare's inaccurate portrayal of MacBeth was unintentional, as he only had access to sources written from the point of view of the English and 'Anglicized Scotsmen', detached culturally and linguistically from 11th-century Scotland.

[32] In a 1959 essay, Boris Pasternak compared Shakespeare's characterisation of Macbeth to Raskolnikov, the protagonist of Crime and Punishment by Fyodor Dostoevsky.