On March 24 1603, the Scottish king James VI ascended the English throne as James I, thus uniting the crowns of England and Scotland. It has often been argued that Macbeth, thought to have been one of three plays performed at Hampton Court on 7 Aug 1606 for James and Christian IV of Denmark, is a reflection of the new king's personal and political preoccupation with regicide and kingship. James was something of an authority on the complexities of royal succession and hereditary rights, and had written, amongst others, The True Law of Free Monarchies (1598) which insisted on the divine right of kings, and Basilikon Doron (1599) which was concerned with the distinction between good monarchs and tyrants.
Harrington, Louise. "Macbeth". The Literary Encyclopedia. First published 08 July 2004
[https://www.litencyc.com/php/sworks.php?rec=true&UID=3798, accessed 24 November 2017.]