PART II
POWERS OF COURTS AND SPECIAL AREAS
20A. Information to be supplied on arrest
(1) Subject to subsection (5), where a person is arrested, otherwise than by being informed that he is under arrest, the arrest is not lawful unless the person arrested is informed that he is under arrest at the time of the arrest or as soon as is practicable after his arrest.
(2) Where a person is arrested by a police officer, subsection (1) applies regardless of whether the fact of the arrest is obvious.
(3) Subject to subsection (5), no arrest is lawful unless the person arrested is informed of the reason for the arrest at the time of, or as soon as is practicable after, the arrest.
(4) Where the person is arrested by a police officer, subsection (3) applies regardless of whether the reason for the arrest is obvious.
(5) Nothing in this section shall be deemed to require a person to be informed —
(a) that he is under arrest ; or
(b) of the reason for the arrest, if it was not reasonably practicable for him to be so informed by reason of his having escaped from arrest before the information could be given.
Rights during investigation - informed of belief that crime has been committed
EDIT.