Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 100. Fair Trial Guarantees
Section H. Assistance of an interpreter
The UK Military Manual (1958) provides, regarding disciplinary punishment of a prisoner of war: “If necessary, [the prisoner of war must] be given the services of a qualified interpreter.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 208.
The manual further states: “In any judicial proceedings against him, the prisoner of war is entitled … if he so desires, to have the services of a qualified interpreter.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 227.
With respect to situations of occupation, the manual states:
Unless they voluntarily waive such assistance, accused persons must be aided by an interpreter, both during preliminary investigation and during the hearing in court. They have the right at any time to object to the interpreter and to ask for his replacement. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 571.
The UK LOAC Manual (2004) states in its chapter on the protection of civilians in the hands of a party to the conflict:
Before any disciplinary punishment is awarded, the accused must be given full details of the offence and be given an opportunity to explain his conduct and to defend himself. In particular, he must be allowed to call witnesses and, if necessary, given the services of a qualified interpreter. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.9.
In its discussion on judicial proceedings against prisoners of war, the manual states: “In good time before the trial to enable him to exercise them, the accused must be informed of his rights to … have the services of a competent interpreter.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.133.
In its discussion on disciplinary measures against prisoners of war, the manual states: “Before any disciplinary award is announced, the accused must …, if necessary, be given the services of a qualified interpreter.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.125.
Furthermore, in its discussion on the administration of criminal law in occupied territory, the manual provides that the accused “are entitled to … an interpreter to assist both during the preliminary investigation and at the trial, together with the right to object to the interpreter at any time and to ask for his replacement”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 11.58 11 .
Lastly, in its chapter on internal armed conflict, the manual states: “Indispensable judicial guarantees include as a minimum … the attendance of …, if necessary, an interpreter.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.30.5.