(1) A senior police officer may give an authorisation under subsection (2) or (3) in relation to a specified area or place if the officer—
(a) reasonably suspects that an act of terrorism will take place; and
(b) considers that—
(i) the authorisation is necessary to prevent such an act;
(ii) the specified area or place is no greater than is necessary to prevent such an act; and
(iii) the duration of the authorisation is no longer than is necessary to prevent such an act.
(2) An authorisation under this subsection authorises any constable in uniform to stop a vehicle in the specified area or place and to search—
(a) the vehicle;
(b) the driver of the vehicle;
(c) a passenger in the vehicle;
(d) anything in or on the vehicle or carried by the driver or a passenger.
(3) An authorisation under this subsection authorises any constable in uniform to stop a pedestrian in the specified area or place and to search—
(a) the pedestrian;
(b) anything carried by the pedestrian.
(4) A constable in uniform may exercise the power conferred by an authorisation under subsection (2) or (3) only for the purpose of discovering whether there is anything which may constitute evidence that the vehicle concerned is being used for the purposes of terrorism or (as the case may be) that the person concerned is a person falling within section 40(1)(b).
(5) But the power conferred by such an authorisation may be exercised whether or not the constable reasonably suspects that there is such evidence.
(6) A constable may seize and retain anything which the constable—
(a) discovers in the course of a search under such an authorisation; and
(b) reasonably suspects may constitute evidence that the vehicle concerned is being used for the purposes of terrorism or (as the case may be) that the person concerned is a person falling within section 40(1)(b).
(7) Schedule 6B (which makes supplementary provision about authorisations under this section) has effect.
(8) In this section—
“driver”, in relation to an aircraft, hovercraft or vessel, means the captain, pilot or other person with control of the aircraft, hovercraft or vessel or any member of its crew and, in relation to a train, includes any member of its crew;
“senior police officer” has the same meaning as in Schedule 6B (see paragraph 14(1) and (2) of that Schedule);
“specified” means specified in an authorisation.”