However, routine administration of the military is delegated as a matter of law to the Defence Council of the United Kingdom, a body officially charged with the direction and command of the Armed Forces.

Before joining the military all recruits of the British Armed Forces (other than Officers in the Royal Navy and Royal Marines[9]) must take the following oath: I... swear by Almighty God (do solemnly, and truly declare and affirm) that I will be faithful and bear true allegiance to His Majesty King Charles III, His Heirs and Successors, and that I will, as in duty bound, honestly and faithfully defend His Majesty, His Heirs and Successors, in Person, Crown and Dignity against all enemies, and will observe and obey all orders of His Majesty, His Heirs and Successors, and of the Generals and Officers set over me.

[8]Supreme command and control over the Armed Forces vests in the Sovereign by virtue of the royal prerogative; this constitutional arrangement has existed in the United Kingdom and its successor states since time immemorial.

[11] That notwithstanding, the delegation of daily command authority does not in any way affect the Crown's personal prerogatives in relation to the Armed Forces.

The Prime Minister (in consultation with the Cabinet) makes the key political decisions on the use of the Armed Forces while the Defence Secretary administers daily military operations.

The Sovereign thus enjoys the right to be consulted before acting on ministerial advice, the right to encourage a given course of military action, and the right to warn against or request a reconsideration of the same.

[19][20] In addition, the monarch has a number of reserve powers at his disposal, albeit rarely invoked, to uphold responsible government and prevent unlawful use of the Armed Forces.

His office provides the Monarch with the information and documentation related to defence affairs that he requires to perform his military functions.

This change was implemented in response to the 2011 Levene report, which advised that it would serve to "streamline top-level decision-making, simplify lines of accountability... remove duplication between the posts and also provide impetus to the leaning of the senior leadership".

[8] The King signs a royal warrant directing the issue of the Letters Patent and ordering the Great Seal of The Realm to be affixed to them.

The Secretary of State first makes an informal submission of the name of a candidate, after the Monarch has signified his approval the Defence Ministry prepares the formal Warrant of Appointment.