In 1939 the Royal Navy suffered its worst ever submarine disaster less than 40 miles from where it was built in Birkenhead.
Above, Thetis at Cammell Laird shipyard.
The Fateful Launch.
On 1 June 1939, Thetis left Cammell Laird shipyard at Birkenhead on its maiden voyage, a test run and dive in the home waters of Liverpool Bay. Conditions inside the new ‘T’ class submarine were very cramped, carring 103 personnel, twice the number she was designed to carry. Only 53 were crew, the rest mainly engineers, workmen and Royal Navy observers. The 50 non-crew were given the opportunity to leave the submarine, but all chose to stay on board.
The 270 foot submarine, led out to sea by the tug Grebe Cock, reached its diving position at 2pm, 38 miles from the Port of Birkenhead and 14 miles from Anglesey.
Thetis’s initial dive was to last for three hours, but for 25 minutes the submarine struggled to submerge, apparently being too light, when suddenly she went underwater. On board the submarine the fateful decision was made to allow seawater into the torpedo tubes to add weight.
A few weeks earlier, a painter, working on the other side of the torpedo door, had dripped enamel onto the test cock within the torpedo tube, which solidified, causing the safety feature of indicating if there was seawater in that particular torpedo tube, to be useless.
Without knowing the test cock was blocked, it was believed it was safe to open the rear door of tube number 5, which was in fact full of water, as its outer door was open to the sea, thousands of gallons of water rushed into this forward area and Thetis nosedived and within minutes the bow hit the seabed 160 feet below. Efforts to enter the tube compartment and close the bow cap failed. An S.O.S was sent and the 103 people on board could only wait for help to arrive.
Observers on the Grebe Cock became alarmed by the sudden dive and raised the alarm with the Navy’s Submarine Headquarters in Portsmouth, but it took over three and a half hours for the message to be received.
Eventually a rescue operation was organised and the destroyer Brazen made to the scene and six naval vessels sailed from Scotland to assist the rescue.
A Failed Rescue.
On board, levels of carbon dioxide became dangerously high. Sixty tons of drinking water and fuel were dumped allowing the submarine to rise stern first and the propellor section protrude from the water. Seeing the opportunity, sailors began slipping through an escape hatch at the rear of the vessel, but only four escaped, one at a time. Four other men attempted to escape, but inexplicably opened the outer hatch and the forward door to the engine room at the same time. Seawater rushed in flooding the escape chamber and engine room, pressurising the carbon dioxide into a deadly cloud.
At first, hopes were optimistic and it was unthinkable that the submarine, partly visible above the water could threaten the lives of the remaining 99 on board, not knowing they had already suffocated.
The Liverpool salvage vessel Vigilant managed to secure cables around the protruding stern as rescuers arrived with oxyacetylene cutting equipment and using winches, an effort was made to pull the submarine further out of the water. The strain on the cable was too much, the hawser snapped and the rescuers could only watch Thetis slowly disappear beneath the sea.
The Rescue Is Abandoned.
On Saturday 3rd June 1939, the Admiralty announced that there was no hope of the further rescue of survivors. The bodies of the 99 remained inside the Thetis for four months, when a huge salvage operation raised and dragged then grounded the wreck on the beach at Moelfre Bay, Anglesey. It was 3rd September 1939, the same day Britain declared war on Germany.
Human remains that had not already been removed by the salvage team were now recovered. The bodies were interned in a mass grave at Holyhead, with a memorial dedicated to them.
The loss of the 99 crew and personnel remains the worst submarine disaster in the United Kingdom.
HMS Thetis beached on Anglesey.
Relaunch As HMS Thunderbolt.
The submarine was successfully salvaged and went through an extensive rebuild at Cammell Laird and in 1940 was recommissioned as HMS Thunderbolt beginning a successful and considerable war record.
On 14th March 1943 Thunderbolt left Malta and headed towards the coast of Sicily and attacked an Italian shipping convoy. A number of Italian war ships began to hunt Thunderbolt. Her position was detected and attacked by an Italian corvette which released twenty four depth charges at the submarine with devastating effect. All hands were lost and Thunderbolt sank to the bottom of the Mediterranean Sea, resting in 1350 metres of water, where it lays to this day, as a war grave.
All photos courtesy of Google Images.
Sources of reference included, Secrets of the Red Rose County by Kenneth Fields (Sigma Press 1998).