According to Anglican theology, what is the basis for the phrase "May God save the Queen"?

The phrase “May God save the Queen” (or “...the King,” depending on the reigning monarch) is famously part of the British national anthem and is regularly used in royal ceremonies and public prayers. It reflects a deep-rooted tradition in the United Kingdom, where the monarch also holds the title of Supreme Governor of the Church of England. According to Anglican theology, what is the basis for invoking God’s saving help on the monarch? How does this relate to Anglican understandings of divine providence, the God-ordained nature of civil authority (e.g., Romans 13:1–7), and the Church’s duty to intercede for rulers (e.g., 1 Timothy 2:1–2)? Does this phrase carry a spiritual significance regarding the monarch’s role, or is it mainly a formal civic expression? I’m looking for answers grounded in Anglican theological thought and liturgical practice, rather than purely historical or political explanations.