Abstract: The invention relates to a system for automatic surveillance of a site by recording data collected by a video camera 3 upon the occurrence of an incidental event (e.g. a road accident). The apparatus comprises an accident detector and a video tape recorder equipped with a controller device that causes the recorder to operate on successive sections of the magnetic tape, each section corresponding to a sequence of predetermined length. At the end of recording on each section, the controller determines whether to continue recording images either repeatedly on the same section after returning to the beginning thereof, in the case of there being no accident or, in the case of an accident, recording the images onto the following section. The autonomy of the magnetic tape recorder is thereby considerably increased.