Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 61. Improper Use of Other Internationally Recognized Emblems
The UK LOAC Manual (2004) states: “It is prohibited to … misuse deliberately in an armed conflict other internationally recognized protective emblems, signs or signals, including the flag of truce, and the protective emblem of cultural property.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.10.
The UK Geneva Conventions Act (1957), as amended in 1995, provides:
Subject to the provisions of this section, it shall not be lawful for any person, without the authority of the Secretary of State, to use for any purpose whatsoever any of the following emblems or designations, that is to say –
(d) the sign of an equilateral blue triangle on, and completely surrounded by, an orange ground, being the international distinctive sign of civil defence. 
United Kingdom, Geneva Conventions Act, 1957, as amended in 1995, Section 6(1)(d).
The UK Geneva Conventions Act (1957), as amended in 2009, states:
Use of Red Cross and other emblems.
(1) Subject to the provisions of this section, it shall not be lawful for any person, without the authority of the Secretary of State, to use for any purpose whatsoever any of the following … ; that is to say –
(d) the sign of an equilateral blue triangle on, and completely surrounded by, an orange ground, being the international distinctive sign of civil defence;
(e) any of the distinctive signals specified in Chapter III of Annex I to the first protocol, being the signals of identification for medical units and transports. 
UK, Geneva Conventions Act, 1957, as amended on 2 July 2009, Section 6(1)(d)–(e).
A training video on IHL produced by the UK Ministry of Defence illustrates the rule that the false use of emblems is forbidden. 
United Kingdom, Ministry of Defence, Training Video: The Geneva Conventions, 1986, Report on UK Practice, 1997, Chapter 2.4.