421. Authorisation of custody without charge.

Where a person is arrested1 the arrest, and any grounds on which he is being kept in service custody without being charged with a service offence2, must be reported as soon as practicable to his commanding officer3. Until such a report is made, the person may be kept in service custody without being charged with a service offence, but only if the person who made the arrest has reasonable grounds for believing that keeping him in custody without charge is necessary to secure or preserve evidence relating to an offence for which he is under arrest, or to obtain