Union of the Scottish and English crowns in the context of "Interregnum (1649–1660)"

James VI and I (James Charles Stuart; 19 June 1566 – 27 March 1625) 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 on 24 March 1603 until his death in 1625. Though he long attempted to get both countries to adopt a closer political union, the kingdoms of Scotland and England remained sovereign states, with their own parliaments, judiciaries, and laws, 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. He acceded to the Scottish throne at the age of thirteen months, after his mother was forced to abdicate. Although his mother was a Catholic, James was raised as a Protestant. Four regents governed during his minority, which ended officially in 1578, though he did not gain full control of his government until 1583. In 1589, he married Anne of Denmark. Three of their children survived to adulthood: Henry Frederick, Elizabeth, and Charles. In 1603, James succeeded his cousin Elizabeth I, the last Tudor monarch of England and Ireland, who died childless. He reigned in all three kingdoms for 22 years, a period known as the Jacobean era, until his death in 1625. After the Union of the Crowns, he based himself in England from 1603, returning to Scotland only once, in 1617, and styled himself "King of Great Britain and Ireland". He advocated for a single parliament for England and Scotland. In his reign, the Plantation of Ulster and English colonisation of the Americas began.

Anne of Denmark (Danish: Anna; 12 December 1574 – 2 March 1619) was Queen of Scotland from her marriage to James VI and I on 20 August 1589 and Queen of England and Ireland from the union of the Scottish and English crowns on 24 March 1603 until her death in 1619.

The second daughter of King Frederick II of Denmark and Sophie of Mecklenburg-Güstrow, Anne married James at age 14. They had three children who survived infancy: Henry Frederick, Prince of Wales, who predeceased his parents; Princess Elizabeth, who became Queen of Bohemia; and James's future successor, Charles I. Anne demonstrated an independent streak and a willingness to use factional Scottish politics in her conflicts with James over the custody of Prince Henry and his treatment of her friend Beatrix Ruthven. Anne appears to have loved James at first, but the couple gradually drifted and eventually lived apart, though mutual respect and a degree of affection survived.