It is a subsidiary test evolved by the court for the purpose of determining the main question whether the past activities of the detenu is such tat from it a reasonable prognosis can be made as to the future conduct of the detenu and its utility, therefore, lies only in so far as it subserves that purpose and it cannot be allowed to dominate or drown it. 'The prejudicial act of the detenu may in a given case of such a character as to suggest that it is a part of an organised operation of a complex of agencies collaborating to clandestinely and secretly carry on such activities and in such a case the detaining authority may reasonably feel satisfied that the prejudicial act of the detenu which has come to light cannot be a solitary 'or isolated act, but must be part of a course of conduct of such or similar activities clandestinely or secretly carried on by the detenu and it is, therefore, necessary to detain him with a view to preventing him from indulging in such activities in the future.