By 1536, Henry VIII had broken with Rome, seized the Church's assets in England and declared the Church of England as the established church with himself as its head. The Act of Supremacy 1534 confirmed the King's status as having supremacy over the church and required the peers to swear an oath recognising Henry's supremacy. Henry's daughter, Mary I, attempted to restore the English Church's allegiance to the Pope and repealed the Act of Supremacy in 1555. Elizabeth I ascended to the throne in 1558 and the next year Parliament passed the Act of Supremacy 1558 that restored the original act. To placate critics, the Oath of Supremacy which peers were required to swear, gave the monarch's title as Supreme Governor rather than Supreme Head of the church. This wording avoided the charge that the monarchy was claiming divinity or usurping Christ, whom the Bible explicitly identifies as Head of the Church.
"Defender of the Faith" (Fidei Defensor) has been part of the English (and since the Union of Scotland and England, British) monarch's title since Henry VIII was granted it by Pope Leo X in 1521 in recognition of Henry's role in opposing the Protestant Reformation. The pope withdrew the title, but it was later reconferred by Parliament in the reign of Edward VI.
This royal role is acknowledged in the Preface to the Thirty-Nine Articles of 1562. It states that:
"Being by God's Ordinance, according to Our just Title, Defender of the Faith and Supreme Governor of the Church, within these Our Dominions, We hold it most agreeable to this Our Kingly Office, and Our own religious zeal, to conserve and maintain the Church committed to Our Charge, in Unity of true Religion, and in the Bond of Peace ... We have therefore, upon mature Deliberation, and with the Advice of so many of Our Bishops as might conveniently be called together, thought fit to make this Declaration following ... That We are Supreme Governor of the Church of England ... "
Article 37 makes this claim to royal supremacy more explicit: