Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 99. Deprivation of Liberty
Section C. Prompt information on the reasons for deprivation of liberty
The UK LOAC Manual (2004) states in its chapter on the protection of civilians in the hands of a party to the conflict: “Where a person is arrested, detained or interned ‘for actions related to the armed conflict’, he must be informed promptly in a language which he understands of the reason for these measures.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.5.
In 2004, in a reply to a question concerning persons detained in Iraq, the UK Foreign and Commonwealth Office stated: “The prison conditions are in accordance with the Geneva Conventions. All internees are informed of the reason for their detention as stipulated by the fourth Geneva Convention.” 
United Kingdom, Letter to the Clerk from the Parliamentary Relations and Devolution Department, Foreign and Commonwealth Office, 24 June 2004, published in House of Commons Foreign Affairs Committee, Foreign Policy Aspects of the War Against Terrorism: Seventh Report of the Session 2003–04, Vol. II: Oral and Written Evidence, HC 441-II.