James VI and I (James Charles Stuart) was King of Scotland as James VI from 24 July 1567 and King of England and Ireland as James I from the union of the Scottish and English crowns in 1603 until his death in 1625. The kingdoms of Scotland and England were individual sovereign states, with their own parliaments, judiciaries, and laws, though both were ruled by James in personal union. James was the son of Mary, Queen of Scots, and a great-great-grandson of Henry VII, King of England and Lord of Ireland, and thus a potential successor to all three thrones. James succeeded to the Scottish throne at the age of thirteen months, after his mother was compelled to abdicate in his favour. Four different regents governed during his minority, which ended officially in 1578, though he did not gain full control of his government until 1583. In 1603, he succeeded the last Tudor monarch of England and Ireland, Elizabeth I, who died childless. He continued to reign in all three kingdoms for 22 years, a period known after him as the Jacobean era, until his death (Wikipedia).
J. K. R. Murray, ‘The gold forty-shilling piece of James VI of Scotland’, 38 (1969), 193-94