Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 16. Target Verification
The UK LOAC Pamphlet (1981) states: “Everything feasible must be done to verify that the target is a military objective.” 
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 4, p. 13, § 4(a).
The UK LOAC Manual (2004) states: “There is a legal obligation to do everything feasible to verify that the proposed target is not protected from attack and that it is a military objective.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.32.2.
In its chapter on maritime warfare, the manual provides:
With respect to attacks, the following precautions shall be taken:
a. those who plan, decide upon or execute an attack must take all feasible measures to gather information which will assist in determining whether or not objects which are not military objectives are present in an area of attack;
b. in the light of the information available to them, those who plan, decide upon or execute an attack shall do everything feasible to ensure that attacks are limited to military objectives. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 13.32.
In a report submitted to the UN Security Council on operations in the Gulf War, the United Kingdom asserted that UK commanders were briefed on the “locations and significance of sites of religious and cultural importance in Iraq” and that operations would take this information into account. 
United Kingdom, Letter dated 21 January 1991 to the President of the UN Security Council, UN Doc. S/22115, 21 January 1991, p. 1; see also Letter dated 13 February 1991 to the President of the UN Security Council, UN Doc. S/22218, 13 February 1991, p. 1.
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:
We have no means of ascertaining the numbers of military or civilian lives lost during the conflict in Iraq to date, although we make every effort to keep any impact upon the Iraqi civilian population to an absolute minimum. All our military planning is conducted in full accordance with our obligations under international law to employ the minimum necessary use of force to achieve military effect, and to avoid injury to non-combatants or civilian infrastructure. Practically, this is achieved through a combination of an extremely careful targeting process and highly accurate precision guided weapons. 
United Kingdom, House of Commons, Written answer by the Minister of State for the Armed Forces, Ministry of Defence, Hansard, 2 April 2003, Vol. 402, Written Answers, col. 738W.