19Powers of arrest and seizure by members of Her Majesty’s forces
(1)Any member of Her Majesty’s forces on duty may arrest without warrant, and detain for not more than four hours, a person who he has reasonable grounds to suspect is committing, has committed or is about to commit any offence.
(2)A person effecting an arrest under this section complies with any rule of law requiring him to state the ground of arrest if he states that he is effecting the arrest as a member of Her Majesty’s forces.
(3)For the purpose of arresting a person under this section a member of Her Majesty’s forces may enter and search any premises or other place—
(a)where that person is, or
(b)if there are reasonable grounds for suspecting that that person is a terrorist or has committed an offence involving the use or possession of an explosive substance or firearm, where there are reasonable grounds for suspecting him to be.
(4)Any member of Her Majesty’s forces may seize, and detain for not more than four hours, anything which he has reasonable grounds to suspect is being, has been or is intended to be used in the commission of an offence under section 26 or 27.