As the Church's political grip weakened, kings claimed the mandate directly. 'Divine right of kings' held that monarchs were accountable only to God — not to popes, and certainly not to parliaments. It worked until it didn't.
After losing the English Civil War to Parliament's New Model Army, Charles I was tried by a special High Court of Justice established by the Rump Parliament. He was charged with treason for waging war against his own people. 59 commissioners signed the death warrant. He was beheaded outside the Banqueting House in Whitehall at around 2pm on January 30, 1649. He was the first reigning European monarch to be publicly executed by his subjects after a legal trial. The precedent was unforgettable, even after the monarchy was restored in 1660.
After a 72-year reign — the longest of any European monarch — the Sun King died. His model of absolutism (‘L'État, c'est moi’) was copied across Europe even as its philosophical foundation was already being dismantled by Enlightenment writers.
Parliament invited William of Orange to replace James II. The transition was nearly bloodless. The 1689 English Bill of Rights that followed established Parliamentary supremacy, protected property from arbitrary seizure, and required regular elections. The first modern constitutional monarchy.