HMS Medusa was commissioned as Harbour Defence Motor Launch (HDML) 1387 in 1943 having been constructed in Poole at the yard of R.A. Newman & Sons Ltd (now Sunseeker Yachts). The design for the HDML was drawn up by W.J. Holt who was the Chief Constructor of the Naval Construction Department at the Admiralty. In total 486 HDMLs of this type were constructed. They were built in batches of ten by a multitude of small, commercial boat-builders scattered around the country. Some were also constructed in United States. Each one was hand-built by craftsmen, and as such no two HDMLs are completely identical.
The HDML was intended principally to act as an offshore screen and to protect harbours and estuaries against submarines, although the coastal threat from German U-Boats never really materialised. The craft were found to be excellent sea-going vessels. They were well armed, and their diesel engines, large fuel capacity and displacement hull gave them a long range which made them useful as convoy escorts. The HDMLs were also fairly quiet ships thanks to their low speed diesel engines, and this proved vital in their role landing agents.
Following crew training in Scotland, she entered active service. In the spring of 1944 she was fitted with a variety of special equipment prior to her involvement in the Normandy landings. This included the GEE navigator system (known in the navy as "QH"), the Decca (or "QM") system, 78T Radio Beacon and the FH-830 Acoustic Beacon. The equipment was state-of-the-art for its day and required the crew undergo special training. Only two HDML craft were fitted Decca system.
In May 1944, HDML 1387 took part in Exercise Fabius. Split over a number of locations along the south coast, Fabius was the largest amphibious training exercise of the war. It took place just a week after the disastrous Exercise Tiger. She took part in the element known as "Fabius 1" which was a practice assault by elements of the American 1st and 29th Infantry Divisions (Task Force O). Her role was to help protect the forces from expected German air, surface and submarine attacks. Along with ML 1387 were 17 other vessels of the Coastal Force, plus 9 US Navy Destroyers, 2 US Navy Destroyer Escorts, 6 Royal Navy Destroyers, 10 US Navy Patrol Craft, 9 Frigates and 3 Trawlers. "Fabius 1" ran between 3rd and 8th May and involved around 25,000 troops. Afterwards, most of the units that participated went straight to their marshalling areas.
On D-Day itself, HDML 1387 formed part of the 149th ML Flotilla. On the 5th June she set up station at position 50 05N 000 46 44W above one of the beacons laid during Operation Enthrone a few nights earlier. Her Type 134 Asdic equipment received the signal from the seabed and was used to navigate ML 1387 into the correct position. She would spend the next 30 hours in this spot, marking one of the two approach channels towards Omaha beach. The operational orders from D-Day read: "HDML 1383 and HDML 1387 are identified as the Channel Identification Group. They are to proceed from Portland independently in time to reach Approach Channels 3 and 4 respectively by H Hour - 13. The approaches are marked by FH 830 acoustic beacons previously laid by ML 147, ML 151 and ML 198 Operation Enthrone. HDML 1383 and HDML 1387 are to transmit 3 or 4 as appropriate at 30 second intervals on a shielded blue signal lamp through the night. By day they are to fly a large international code numeral flag. HDML 1383 and HDML 1387 are to remain on station until 2300 on D-Day".
Her job was to mark the entrance to the German minefield that had been laid off the coast of Normandy. On the night before D-Day, minesweepers approached her position and began cutting a clear channel through the mine field. HDML 1387'-s exact position was critical. She would mark the centre of one of the two clear channels for elements of the approaching invasion fleet of Task Force O heading towards Omaha Beach. After the initial landings she continued to the assault anchorage and was used to distribute instructions to other units before returning to Portsmouth to operate as a convoy escort. Some days later, after escorting a convoy of block-ships to Juno Beach in bad weather, she was damaged and began taking on water. She returned to dry-dock in Portsmouth for repairs - being kept afloat only by the use of hand and power pumps.
Later in the war in she was at the Dutch port of Ijmuiden which was full of German soldiers waiting to surrender. The German surrender was received aboard ML 1387. Ashore, a sentry had been posted dressed in his best uniform. As he patrolled the quayside he managed to drop the vessel's only rifle into the harbour after accidentally tripping over a mooring line.
HDML 1387 was the last of her class to remain in service. She was eventually discharged from military service in 1968 as "Medusa", having undergone a number of name changes during her years of service. She spent time in the private hands of various groups and individuals. In 1977 she briefly entered military entered once again. She was chartered for a military exercise and transported SAS Reservists and soldiers of the Territorial Army to Worbarrow Bay in Dorset for a night assault.
Today she is a member of the National Historic Fleet, being preserved and operated by The Medusa Trust. In 2006 the Trust received Heritage Lottery Funding of £1m for a much needed restoration of the vessel which was originally designed to have just a five year operational life span. Medusa was practically rebuilt from the keel up in a project that took four years to complete. When she re-entered the water in 2010, a rededication ceremony was held in Portsmouth Naval Base and was attended by HRH The Princess Royal. Although several others survive, almost unrecognisable, as houseboats, HMS Medusa is the last of these little ships in original sea-going condition. For more information please visit The Medusa Trust.