Why must the British monarch act on the advice of ministers?

In the United Kingdom’s constitutional monarchy, the monarch acts on the advice of ministers because political power rests with the prime minister and the cabinet, who are accountable to Parliament.1

This arrangement is rooted in the principle of ministerial responsibility, which evolved over centuries to ensure the government remains answerable to the legislature rather than the sovereign. Historically, Parliament asserted its power by making ministers responsible for government actions, effectively using the maxim that "the king can do no wrong" to prevent the monarch from shielding ministers from parliamentary criticism.2

Today, the monarch’s role is primarily symbolic, representing the unity of the state. While the sovereign formally appoints the prime minister and performs ceremonial duties, they do not exercise substantive political power. Because the government must maintain the confidence of the House of Commons to remain in office, the monarch is constitutionally bound to follow the advice of the ministers who command that support.3421