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The Police and Criminal E v idence Act (1984) sets out the following principles for an arrest to be lawful. Note that an arrest is unlawful, regardless of the procedure followed, if there is no Power of arrest for the offence in question.

• s.28 of PACE requires that the arrestee whould be told in unequivocal terms (i) that he is under arrest, and (ii) why he is under arrest. If the arrestee was not told of his arrest at the time it was made (e.g., he was locked in a car by an automatic mechanism) he should be told as soon as practicable, and given the reasons. A person should not be allowed to infer incorrectly that he has been arrested when he has not.
• Reasonable force, and detention, may be used. These may include forcible restraint, or being locked inside a room. If a person is old or frail, then such tactics will generably regarded as unreasonable; similarly, an arrest of a person who is already in a police station should not require forcible restraint.
• The PACE Detention Code indicates that a person arrested should be cautioned as soon as possible that anything has says may be used as evidence.
• PACE s.30 requires that an arrested suspect should be taken to a police station as soon as practical, rather than being questioned on the spot. However, it allows that such action can be delayed if it would prejudice an investigation or the recovery of stolen goods.
• s.30 also indicates that the police station used should be one designated for the detention of arrested suspects; again, however, it allows this requirement to be relaxed where there is no such station available.