IT was in this week 77 years ago that the largest single loss of life involving a shipwreck in the Firth of Clyde took place.

On March 27, 1943, HMS Dasher suffered a massive internal explosion and the converted aircraft carrier quickly sank with the loss of 379 men of her 528-strong crew.

To this day, the cause of the ship’s sinking remains a matter of speculation, though continuing reports that she was sunk by a torpedo from a German U-boat can be discounted as the German Navy never claimed responsibility, and their records show that no U-boat was in the area at the time.

HMS Dasher was originally a merchant ship called Rio de Janeiro, one of four “Rio” class passenger-cargo vessels built by the Sun Shipbuilding company at Chester.

She was launched on April 12, 1941, and requisitioned by the US Navy for conversion to an escort carrier. The work was carried out at a New Jersey shipyard and in a lend-lease deal she was commissioned into the Royal Navy in July, 1942.

After conversion – a wooden flight deck was installed on her superstructure and defensive guns were installed – the re-named HMS Dasher sailed across the Atlantic without incident.

Dasher weighed 8200 tons and had a crew of 555. With a capacity for 15 aircraft, usually Sea Hurricanes or Swordfish biplanes, she first saw service in the Mediterranean in the operation to support the Allies’ landings in Operation Torch, the invasion of Northern Africa in November, 1942.

Dasher was next assigned to Arctic convoy duty, and on February 16, 1943, she sailed with five Sea Hurricanes and six Swordfishes to cover convoy JW53 on its trip to Russia via Iceland.

Off Iceland, a fierce storm enveloped the convoy and Dasher was badly damaged. The convoy continued and returned from Russia with no loss of personnel.

Dasher went to Dundee for repairs and then headed for the Firth of Clyde for exercises.

Her new captain, Lennox Albert Knox Boswell, had been in charge for just three weeks when he commanded the carrier in flying exercises on Saturday, March 27.

The next operation that Dasher was preparing for was a torpedo strike against the German battleship Tirpitz and for the exercise she was both fully fuelled with 75,000 gallons of ship oil and 20,000 gallons of aircraft fuel – and carried more than 100 depth charges and at least six torpedoes.

At 4.40pm Boswell announced that the exercise was complete and the ship was going to return to Greenock where the crew would be able to have shore leave.

The Royal Navy Research Archive gives details of what happened next: “Shortly after this there was a tremendous explosion; the officers on the bridge looked in astonishment as the ship’s two-ton aircraft lift flew about 60 feet into the air before it fell into the sea behind the ship.

“Dasher lurched drunkenly before settling by the stern as she began to take on water. The ship quickly lost headway as the engines had stopped, and all electrical power was lost, below decks being plunged into darkness. The now exposed lift shaft was belching thick black smoke and flames.

“Those men not part of the duty watch had already begun preparing for their return to port and the imminent run ashore. They were plunged into disorienting darkness where they stood.

“Those that could make their way out of the ship began abandoning ship, jumping overboard from any point of exit they could reach as the fires in the hanger deck grew more intense and the ready use ammunition began to ‘cook off’.”

With oil burning on the water of the Firth, the crewmen who had jumped overboard now faced a terrible dilemma – swim away and risk hypothermia or stay and be swallowed up by the flames.

Two naval vessels and two merchant ships were first on the scene, the SS Lithium rescuing 66 men though some later died.

Other ships headed out from ports around the Firth to help in the rescue but the ship had gone down so quickly – witnesses estimated seven or eight minutes – that there was little chance of survival for those deep within the Dasher.

The government in London ordered a complete news blackout, and families were told only that their loved ones were missing, presumed lost.

Only a dozen of the dead sailors were buried at Ardrossan, while the corpses of at least 68 other victims are believed to have been buried in a secret mass grave.

Survivors, including Boswell, were ordered not to talk about the Dasher.

SEVERAL mysteries surround the sinking.

Some of the more fanciful theories about its cause involved sabotage during the Dundee repairs, while the “truth” as decreed in a Naval inquiry was somewhat more prosaic – poor design by the Americans, who responded by blaming the Royal Navy’s poor handling of the fuel on board.

Again a cover-up was ordered as the War Cabinet of Winston Churchill were concerned that the crucial Lend Lease operations might suffer.

The authors John and Noreen Steele, in their book about the Dasher, indicate that the carrier was a disaster waiting to happen with fuel splashing around the vessel – significantly, the other converted Rio class ships had alterations soon afterwards and the amount of fuel on board them was significantly reduced.

It seems that a lighted cigarette in a fuelling area was most likely to blame.

The other mystery is that of Dasher crew member John “Jack” Melville who drowned in the Firth.

Operation Mincemeat, the famous deception operation that convinced the Germans that the Allies would not attack Sicily, required the body of a drowned man to masquerade as Major William Martin.

Though some argue that it was a Welsh alcoholic Glyndwr Michael, the timing of Mincemeat indicated that the body of Melville or another Dasher sailor may have been used.

The wreck of HMS Dasher lies 500ft down in the Firth of Clyde, roughly halfway between Ardrossan and Arran. The site is a protected war grave.