Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 121. Location of Internment and Detention Centres
The UK Military Manual (1958) states: “Internment camps must be outside the combat zone.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 147.
The manual also provides: “Prisoners of war may be interned only in premises which are on land and which are in every way healthy and hygienic.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 146.
The UK LOAC Pamphlet (1981) states: “PW [prisoner of war] camps must be located on land, not in prison ships, and afford every guarantee of hygiene and health.” 
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, p. 30, § 16(a).
The UK LOAC Manual (2004) states in its chapter on the protection of civilians in the hands of a party to the conflict:
The detaining power must take all necessary and possible measures to ensure that protected persons are, from the outset of their internment, “accommodated in buildings or quarters which afford every possible safeguard as regards hygiene and health, and provide efficient protection against the rigours of the climate and the effects of the war.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.38.
On prisoners of war, the manual states:
As soon as possible after capture, prisoners of war must be evacuated to camps far enough from the fighting to be out of danger. Only those who because of wounds or sickness would run greater risks by being moved than by remaining where they are may be kept temporarily in a danger zone. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.35.
The manual further states: “Camps must be on land and in places which are healthy, hygienic and out of danger.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.37.
The manual also explains: “Prisoners of war must be protected to the same extent as the civilian population from the dangers of war including the provision and use of shelters”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.39.
With regard to internal armed conflicts in which the 1977 Additional Protocol II is applicable, the manual provides:
Those responsible for the internment or detention are also placed under obligation “within the limits of their capabilities” to “respect” some further provisions relating to persons interned or detained for reasons relating to the armed conflict. These are:
c. that places of internment and detention shall not be located close to the combat zone. Protected internees and detainees shall be evacuated when the places where they are interned or detained become particularly exposed to danger arising out of the armed conflict, if their evacuation can be carried out under adequate conditions of safety. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.41.c.
In 2003, in reply to a written question in the House of Commons, the UK Minister of State for the Armed Forces, Ministry of Defence, wrote:
Upon being taken prisoner, Iraqi combatants are evacuated to a safe location, away from the dangers of combat, as soon as is practicable. They are held initially at collection points by the unit taking them prisoner, where their identity is established and recorded. They are then transferred to a more permanent holding facility. 
United Kingdom, House of Commons, Written answer by the Minister of State for the Armed Forces, Ministry of Defence, Hansard, 14 April 2003, Vol. 403, Written Answers, col. 572W.
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:
12. The treaties setting out rules of IHL are supplemented by rules of customary international law (CIL), i.e. rules which are recognized as binding by States, even though they do not appear in treaty texts. … [I]n relation to the rules described below the Government accepts that they reflect CIL. It is suggested that the rules which are of most relevance to this inquiry are:
12.15 … Persons deprived of their liberty must be held in premises which are removed from the combat zone and which safeguard their health and hygiene. 
United Kingdom, Ministry of Defence, Closing Submissions to the Baha Mousa Public Inquiry on Modules 1–3, 25 June 2010, §§ 12 and 12.5, pp. 28 and 32.
[emphasis in original]