7. Prerogative power: relationship with legislation & constitutional conventions


The royal prerogative is essentially what remains of the absolute power that was previously exercised by the Monarch.  This common law power has been eroded over centuries by judicial decisions and legislation.


Some prerogatives are exercised by or in the name of the Crown, such as giving Royal Assent to bills, but others are exercised on behalf of the Crown, by the Prime Minister and other ministers, such as the making of treaties.

Examples of existing prerogative powers are:

  • Foreign affairs:
    • Recognising foreign states.
    • Entering into treaties.
    • Declaring war and deploying armed forces overseas.
  • Domestic affairs:
    • Summoning a Parliament.
    • Appointing and dismissing the Prime Minister and other government ministers.
    • Giving Royal Assent to bills.
    • Defending the real such as by deploying armed forces within the UK.
    • Granting public honours.
    • Setting up public bodies to disburse funds made available by Parliament.

In practice, many prerogative powers need Parliament’s assent because, for example: (i) by convention a Prime Minister is appointed because he commands the confidence of the House of Commons and (ii) the spending of money pursuant to an exercise of prerogative powers will require Parliament’s assent.

Prerogative and statute

Existing royal prerogatives can be abrogated or diminished by statute explicitly or implicitly:

  • Explicitly: with clear statutory wording that states that the prerogative has been abrogated or diminished.
  • Implicitly: with a statute that does not explicitly address the prerogative but which nevertheless covers the whole ground of the prerogative so that it is clear that Parliament intended the prerogative to yield to the new statutory regime.  This principle was established by De Keyser’s case in 1920 when the House of Lords held that the Defence Act 1842, that authorised requisitioning with compensation, had abrogated the prerogative that authorised requisitioning without compensation.[1]  The effect of a statute in cases like this is one of statutory interpretation: what did Parliament intend?  Some statutes will address an issue covered by a royal prerogative in such a way that a new statutory power can co-exist with an existing prerogative.[2]  This will usually be the result where the statutory power is not inconsistent with the continuation of the prerogative power.

In a nod to modernity it has been said that ‘it is 350 years and a civil war too late for the Queen’s court’s to broaden the prerogative.’[3]  However, prerogatives that have merely lain in abeyance, can be revived.  For example, the Fixed-term Parliaments Act 2011 ‘stopped’ the royal prerogative of dissolving Parliament (something exercised by convention at the request of the Prime Minister) in favour of fixed-term 5-year parliaments.  However, subsequent legislation has made the prerogative ‘exercisable again’.[4]  In other words the Act of 2011 merely put the power in abeyance and the Act of 2022 has revived it.

Prerogative and constitutional conventions

The way in which a royal prerogative is to be exercised is frequently governed by conventions that enable the prerogative to be exercised in a way that is consistent with a democracy.  Thus the prerogative to:

  • appoint a Prime Minister, is subject to a convention that the King will appoint the party leader who commands a majority in the House of Commons,
  • appoint and dismiss ministers, is subject to a convention the King will appoint and dismiss ministers on the advice of the Prime Minister,
  • dissolve a Parliament, is only exercised when the King is requested to do so by the Prime Minister,
  • turn bills into acts that have legal force, is subject to a convention that the Royal Assent will be given whenever a bill has passed the necessary procedural requirements.

[1] De Keyser’s Royal Hotel [1920] AC 508, HL.

[2] See, for example, R v Secretary of State for the Home Department ex p Northumbria Police Authority [1989] QB 26, CA, where the prerogative to maintain the Queen’s Peace and keep law and order was not abrogated by the Police Act 1964 which gave police authorities the power to supply equipment, such as plastic bullets, to local police forces.  Accordingly, under the Home Secretary could give plastic bullets to local police forces under the prerogative, by bypassing a police authority.

[3] BBC v Johns [1965] Ch 32 @79.

[4] The Dissolution and Calling of Parliament Act 2022, s2(1).