Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 100. Fair Trial Guarantees
Section C. Presumption of innocence
The UK LOAC Manual (2004) states in its chapter on the protection of civilians in the hands of a party to the conflict:
In the case of penal offences relating to the armed conflict, the basic principles of natural justice must be observed … These principles include the following: … anyone charged with an offence is presumed innocent until proved guilty according to law. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.6.
In its chapter on internal armed conflict, the manual states: “Indispensable judicial guarantees include as a minimum … the presumption of innocence until proved guilty.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.30.5.
In 2008, the UK Army published the Aitken Report which investigated cases where members of the British Army were alleged or proven to have mistreated or killed Iraqi civilians outside the context of immediate combat operations in 2003 or early 2004. The report stated:
27. Four cases involving Iraqi deaths as a result of deliberate abuse have been investigated, and subsequently referred to the Army Prosecuting Authority (APA) on the basis there was a prima facie case that the victims had been killed unlawfully by British troops. …
29. The absence of a single conviction for murder or manslaughter as a result of deliberate abuse in Iraq may appear worrying, but it is explicable. Evidence has to be gathered … ; that evidence has to be presented in court; and defendants are presumed innocent unless the prosecution can prove its case beyond reasonable doubt. 
United Kingdom, Army, The Aitken Report: An Investigation into Cases of Deliberate Abuse and Unlawful Killing in Iraq in 2003 and 2004, 25 January 2008, §§ 27 and 29.
[footnote in original omitted]