HMS Sidon (P259): A Peacetime Tragedy at Portland

Constructed at Birkenhead, Serving Through the War's Final Months

HMS Sidon was built by Cammell Laird at Birkenhead, laid down in July 1943, launched in September 1944 and commissioned that November, an Improved S-class submarine that deployed to the Far East in the spring of 1945, reaching Trincomalee that May and going on to rescue a downed American airman during a war patrol in the south west Pacific before Japan's surrender brought the fighting to a close.

She was present for the reoccupation of Hong Kong before returning home to be paid off at the very end of that year.

A Decade of Ordinary Peacetime Service

Recommissioned for peacetime service, Sidon underwent a series of refits and modernisations through the late 1940s and early 1950s, including the fitting of a snorkel mast and radar, and took her place among the fleet at the Coronation Review of 1953. There was nothing in this decade of routine service to suggest the tragedy that awaited her.

The Explosion

On the morning of 16 June 1955, moored alongside her depot ship HMS Maidstone at Portland, Sidon was preparing to load a new type of experimental torpedo for forthcoming trials, a high test peroxide fuelled weapon known as the Fancy, or Mark 12.

At around 8.25am, an explosion tore through a torpedo loaded in the number three tube, the result, investigators later concluded, of the weapon's starting mechanism being accidentally engaged while it remained enclosed inside the tube, causing its volatile fuel system to rupture.

The resulting chemical reaction and fire breached two watertight bulkheads, filling the forward part of the boat with flame and toxic fumes that killed most of the men in that section almost instantly. Sidon sank by the bow at 8.45am, roughly twenty minutes after the initial blast, settling in shallow water while still tied up alongside.

A Doctor Who Would Not Stop Trying

Thirteen men in total lost their lives. Twelve were killed in the immediate explosion and fire, and the thirteenth was Temporary Surgeon Lieutenant Charles Rhodes, the medical officer of HMS Maidstone, who repeatedly entered the smoke filled, flooding submarine to treat and rescue injured crewmen, ultimately dying himself after using an escape apparatus he had never been trained to operate.

He was posthumously awarded the Albert Medal for gallantry in saving life at sea, a recognition that speaks to the genuine, selfless courage he showed in the accident's chaotic final minutes. Parliament was told on the day itself that a further eight men, one officer and seven ratings, had been injured and hospitalised, out of fifty six personnel aboard in total, meaning forty three survived.

This was a genuine, devastating loss of life in peacetime, and deserves to be remembered with exactly the same seriousness and respect as any wartime casualty.

An Inquiry, and a Withdrawn Weapon

A formal court of inquiry, convened in the immediate aftermath, is reported to have cleared Sidon's own crew of any blame, attributing the disaster instead to a fundamental design fault in the experimental torpedo itself rather than any error by those aboard.

Further problems with the same high test peroxide torpedo programme surfaced again later that year, and the weapon was ultimately withdrawn from service before the end of the decade, a quiet but significant consequence of the tragedy at Portland.

A Wreck That Remains

Sidon was raised about a week after sinking but found to be damaged beyond economical repair, and was never returned to service.

She was deliberately sunk again two years later, in June 1957, to serve as a sonar training target off Portland, and her wreck remains there to this day, now a well known site for recreational divers exploring the waters off Weymouth, a quiet resting place for a submarine whose story is defined, in the end, not by any battle, but by a single, tragic accident in peacetime and the genuine courage shown in its aftermath.