89Power to stop and question
(1)An officer may stop a person for so long as is necessary to question him to ascertain—
(a)his identity and movements;
(b)what he knows about a recent explosion or another recent incident endangering life;
(c)what he knows about a person killed or injured in a recent explosion or incident.
(2)A person commits an offence if he—
(a)fails to stop when required to do so under this section,
(b)refuses to answer a question addressed to him under this section, or
(c)fails to answer to the best of his knowledge and ability a question addressed to him under this section.
(3)A person guilty of an offence under this section shall be liable on summary conviction to a fine not exceeding level 5 on the standard scale.
(4)In this section “officer” means—
(a)a member of Her Majesty’s forces on duty, or
(b)a constable.