Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 111. Protection of the Wounded, Sick and Shipwrecked against Pillage and Ill-Treatment
The UK Military Manual (1958) states that the wounded and sick must be protected against pillage and ill-treatment. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 342.
The manual refers to:
a special class of war crime that is sometimes known as “marauding”. This consists of ranging over battlefields and following advancing or retreating armies in quest of loot, robbing, maltreating and killing stragglers and wounded and plundering the dead – all acts done not as a means of carrying on the war but for private gain. Nevertheless, such acts are treated as violations of the law of war. Those who commit them, whether civilians who have never been lawful combatants, or persons who have belonged to a military unit, an organised resistance movement or a levée en masse, and have deserted and so ceased to be lawful combatants, are liable to be punished as war criminals. They may be tried and sentenced by the courts of either belligerent. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 636.
The UK LOAC Pamphlet (1981) refers to Article 15 of the 1949 Geneva Convention I and states that combatants shall prevent the wounded and sick from being despoiled. 
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 6, p. 22, § 3.
The UK LOAC Manual (2004) states:
The parties to a conflict are under an obligation “at all times, and particularly after an engagement … without delay [to] take all possible measures to search for and collect the wounded and sick, to protect them against pillage and ill-treatment, and to ensure their adequate care”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 7.4; see also § 13.129 (maritime warfare).
With regard to internal armed conflicts in which the 1977 Additional Protocol II is applicable, the manual states:
“Whenever circumstances permit, and particularly after an engagement, all possible measures shall be taken without delay to search for and collect the wounded, sick and shipwrecked, to protect them against pillage and ill-treatment …”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.44.
The UK Army Act (1955), as amended in 1971, provides:
Any person subject to military law who –
(a) steals from, or with intent to steal searches, the person of anyone … wounded … in the course of warlike operations, or … injured … in the course of operations undertaken by Her Majesty’s forces for the preservation of law and order or otherwise in aid of the civil authorities … shall be guilty of looting. 
United Kingdom, Army Act, 1955, as amended in 1971, Section 30(a).
[emphasis in original]
The UK Air Force Act (1955), as amended in 1971, provides for the punishment of any person subject to air force law who:
steals from, or with intent to steal searches, the person of anyone … wounded … in the course of warlike operations, or … injured … in the course of operations undertaken by Her Majesty’s forces for the preservation of law and order or otherwise in aid of the civil authorities. 
United Kingdom, Air Force Act, 1955, as amended in 1971, Section 30(a).
The UK Armed Forces Act (2006) states:
4 Looting
(1) A person within subsection (4) commits an offence if, without lawful excuse –
(a) he takes any property from a person who has been killed, injured, captured or detained in the course of an action or operation of any of Her Majesty’s forces or of any force co-operating with them; or
(b) he searches such a person with the intention of taking property from him.
(4) A person is within this subsection if he is –
(a) a person subject to service law; or
(b) a civilian subject to service discipline. 
United Kingdom, Armed Forces Act, 2006, Section 4.
In 2010, in its closing submissions to the public inquiry into the circumstances surrounding the death of Baha Mousa and the treatment of those detained with him by UK armed forces in Iraq in 2003, the UK Ministry of Defence stated regarding common Article 3 of the 1949 Geneva Conventions: “On its face this protection is restricted to armed conflicts not of an international character. However, it is understood to apply in all forms of armed conflict as part of customary international law to set out the irreducible minimum standard.” 
United Kingdom, Ministry of Defence, Closing Submissions to the Baha Mousa Public Inquiry on Modules 1–3, 25 June 2010, § 10.2, p. 10.
The UK Military Manual (1958) provides: “The civilian population must respect the wounded and sick, and refrain from offering them violence.” The manual further provides: “Nursing the wounded and sick should not be penalised, though this immunity does not extend to the concealment of enemy personnel or the activities of escape organizations.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 345.