A down-the-hole hammer drill bit retaining assembly is arranged to releasably retain a drill bit at a hammer arrangement of a percussion drilling apparatus. The retaining assembly includes a drive sub and a retainer ring. The drive sub has at least one indent to provide a fluid communication pathway for a flushing fluid extending over a radially outward facing surface of the retainer ring and into an internal region of the drive sub in contact with inwardly projecting splines.