Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 56. Freedom of Movement of Humanitarian Relief Personnel
The UK LOAC Manual (2004) states:
Relief personnel may, where necessary, accompany relief consignments, “subject to the approval of the Party in whose territory they will carry out their duties”. They are entitled to respect and protection and parties are under an obligation to assist them “to the fullest extent practicable”. Only “imperative military necessity” can justify any limitation on their activities or restriction of movement, which must in any event be temporary. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.13.