Règle correspondante
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 116. Accounting for the Dead
Section C. Marking of graves and access to gravesites
The UK Military Manual (1958) provides that graves “must be marked so that they may always be found”. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 383.
The UK LOAC Manual (2004) states:
7.36. Graves must be respected and properly maintained. They must be marked so that they may always be found … Graves registration services must be officially established at the outbreak of hostilities and, as soon as circumstances permit, the adverse parties and any other concerned authorities are required to seek agreement for:
b. Access to those grave sites by relatives of the deceased and the representatives of the official graves registration services. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 7.36.