police arresting power- rights of the suspect

Question 1

under s24 police and criminal evidence act 1984 (PACE), what can the police do?

Answer 1

lawfully arrest a suspect without a warrent from a court

Question 2

under s24 PACE ppolice can lawfully arrest a suspect without a warrant but on what grounds?

Answer 2

involved/ attempted to be involved/ suspected of being involved in committing an offence
AND
officers have reasonable grounds to beleive that the arrest is necessary