§ Mr. Lidington
To ask the Secretary of State for the Home Department what powers a constable in England and Wales has to arrest, without warrant, a person on the grounds that he is about to commit a criminal offence; and in respect of which criminal offences such powers exist. 
§ Mr. Charles Clarke
Under section 24 of the Police and Criminal Evidence Act 1984 (PACE) a constable in England and Wales has the power to arrest, without warrant, a person whom he has reasonable grounds for suspecting to be about to commit an arrestable offence. Arrestable offences are defined in sub-sections 24 (1) and (2) of PACE. I am aware that there may be other offences outside the PACE definition which attract the relevant power and I will write to the hon. Member once that aspect has been researched.