Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 88. Non-Discrimination
Section D. Persons deprived of their liberty
The UK Military Manual (1958) prohibits discrimination in the treatment of prisoners of war and restates the provisions of common Article 3 of the 1949 Geneva Conventions. The Military Manual also quotes Article 14 of the 1949 Geneva Convention III. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, §§ 39 and 133.
The UK LOAC Pamphlet (1981) prohibits discrimination in the treatment of prisoners of war and restates the provisions of common Article 3 of the 1949 Geneva Conventions. 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 8, §§ 2 and 9.
The UK LOAC Manual (2004) states:
Prisoners of war must be humanely treated and their persons and honour respected at all times. “Women shall be treated with all the regard due to their sex and shall in all cases benefit by treatment as favourable as that granted to men.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.28.
The manual further states:
There must be no adverse discrimination towards prisoners of war based on race, nationality, religious belief, political opinions or similar criteria. However, the detaining power is permitted to allow privileged treatment to prisoners of war by virtue of their rank, state of health, age or professional qualifications as well as the special rules already mentioned relating to women. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.31.
In its chapter on internal armed conflict, the manual restates the provisions of common Article 3 of the 1949 Geneva Conventions:
Under the terms of Common Article 3, the parties to a non-international armed conflict occurring in the territory of a party to the Conventions are obliged to apply ‘as a minimum’, the following provisions:
(1) Persons taking no active part in the hostilities, including members of armed forces who have laid down their arms and those placed hors de combat by sickness, wounds, detention, or any other cause, shall in all circumstances be treated humanely, without any adverse distinction founded on race, colour, religion or faith, sex, birth or wealth, or any other similar criteria. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.4.