secure many of our rights and privileges; but the great bulk of our constitutional liberties and ... our constitutional practices do not derive their validity and sanction from any Bill which has received the formal assent of the King, Lords and Commons. They rest on usage, custom, convention, often of slow growth in their early stages, not always uniform, but which in the course of time received universal observance and respect. The relationships between the prime minister and the sovereign, Parliament and Cabinet are defined largely by these unwritten conventions of the constitution. Many of the prime minister's executive and legislative powers are actually royal prerogatives which are still formally vested in the sovereign, who remains the head of state. Despite its growing dominance in the constitutional hierarchy, the premiership was given little formal recognition until the 20th century; the legal fiction was maintained that the sovereign still governed directly. The position was first mentioned in statute only in 1917, in the schedule of the Chequers Estate Act. Increasingly during the 20th century, the office and role of prime minister featured in statute law and official documents; however, the prime minister's powers and relationships with other institutions still largely continue to derive from ancient royal prerogatives and historic and modern constitutional conventions. Prime ministers continue to hold the position of First Lord of the Treasury and, since November 1968, that of Minister for the Civil Service, the latter giving them authority over the civil service. Under this arrangement, Britain might appear to have two executives: the prime minister and the sovereign. The concept of "the Crown" resolves this paradox. The Crown symbolises the state's authority to govern: to make laws and execute them, impose taxes and collect them, declare war and make peace. Before the "Glorious Revolution" of 1688, the sovereign exclusively wielded the powers of the Crown; afterwards, Parliament gradually forced monarchs to assume a neutral political position. Parliament has effectively dispersed the powers of the Crown, entrusting its authority to responsible ministers (the prime minister and Cabinet), accountable for their policies and actions to Parliament, in particular the elected House of Commons. Although many of the sovereign's prerogative powers are still legally intact, constitutional conventions have removed the monarch from day-to-day governance, with ministers exercising the royal prerogatives, leaving the monarch in practice with three constitutional rights: to be kept informed, to advise and to warn. Modern premiership