On completion of torqueing up riser to BOP, the yoyo & torque wrench was in the process of being retrieved through the rotary housing to drill floor.
At drill floor level the hook of the yoyo came into contact with the riser clamp & bolt assembly (photo 1) this caused the safety clip of the yoyo to open, dropping the equipment back down to the moonpool area.
The hydraulic hoses x 2 parted at the drill floor.