20. (1) The Minister may give an authorisation where, and only where, he or she—

(a) has received an application under section 21 , and

(b) is satisfied that the conditions referred to in subsection (2) have been met.

(2) The conditions referred to in subsection (1)(b) are:

(a) that there are reasonable grounds for believing that a serious threat exists;

(b) that there is a reasonable prospect that the cessation of a mobile communications service within a geographical area would be of material assistance in averting that threat;

(c) that having regard to all the circumstances, including the importance of maintaining the availability of the mobile communications service in the geographical area concerned and the effect of a cessation on users, the giving of an authorisation is necessary and proportionate to its objectives.