A loaded bulk carrier, Vessel A, was underway in a Traffic Separation Scheme (TSS) in fog, making about 7.6 kts. Visibility was about 350 m, so the Master had put in place a heightened bridge watch regime. The Master had the con, assisted by two other navigation officers, and there was a helmsman at the wheel. Despite these precautions, the bridge team of vessel A was not aware that they were being overtaken by vessel B, behind them. Vessel B’s radar return was intermittent, and Vessel A had not plotted it as a radar target. Vessel B was not emitting an AIS signal. Neither vessel was sounding the one long blast every two minutes required in restricted visibility by the collision regulations. Vessel B was overtaking vessel A at full ahead, making about 11.8 kts. The bridge of vessel B was manned by an OOW and a lookout, with the helm on autopilot. The OOW of vessel B was aware of vessel A, but had not informed the Master of the reduced visibility. Image for representation purposes only Vessel Traffic Services (VTS) contacted vessel A to instruct them to go to anchorage or drift, as visibility in the TSS was too low, and traffic was now suspended. A few minutes later, when the Master saw that the opposite traffic lane was free, he ordered slow ahead on the engine and port helm to cross the lane to comply with the suspension order. The VTS agreed with this alteration, but the VTS operator was also ignorant of the exact position of vessel B, since there was no AIS transmission and the vessel’s radar return was intermittent. Image for representation purposes only The OOW on vessel B became concerned about the developing close quarters situation and called vessel A on the VHF. Vessel A responded, but there was no follow-up conversation. Within seconds, the two vessels were in sight of one another. The Master of vessel A, now realising that vessel B was close behind, ordered hard to starboard to avoid a collision. On vessel B, the OOW put the helm hard to port, but a colli