In the Terrorism Act 2000. By virtue of s. 41(1) “a constable may arrest without a warrant a person whom he reasonably suspects to be a terrorist”.
Section 40 of the Act defines a terrorist as a person who either (a) has committed an offence under certain sections of the Act, or (b) “has been concerned in the commission, preparation or instigation of acts of terrorism”. To the extent that arrest is based on reasonable suspicion of having committed an offence, there is no need for the power under s.41.
Under the Police and Criminal Evidence Act, s. 24,23 a police officer may arrest on reasonable suspicion relating to any offence. It is where the suspicion relates to behaviour falling within (b), that s. 41(1) becomes important and extends the normal arrest powers. . Although acts of “'terrorism” will almost certainly involve the commission of an offence.
So based on the Terrorism Act 200, she can be arrested.
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