HMS Sentinel (P256): A Quiet Career From the Clyde to Gillingham

Constructed at Greenock, Missing the War Entirely

HMS Sentinel was built by Scotts Shipbuilding and Engineering at Greenock, laid down in November 1943, but not launched until July 1945 and not commissioned until the very end of that year, well after Japan's surrender had already brought the Second World War to a close.

She holds the distinction of being one of the small number of S-class submarines completed too late to be employed in any wartime role whatsoever, her entire early career consisting of trials and training off the west coast of Scotland before sailing to Portsmouth in February 1946.

The dates make the point sharper than the sentence does. Her keel was laid on 15 November 1943, when the outcome was not settled and every submarine was wanted. She was launched on 27 July 1945, by which time Germany had been beaten for eleven weeks and Japan had three left. She was completed on 28 December 1945, four months after the surrender. She was ordered for one world and delivered into another. HMS Scorcher and HMS Sea Devil were caught by the same timing.

She was also one of a very great many. The S class ran to sixty-two boats built over fifteen years, fifty of them launched between 1940 and 1945, which makes it comfortably the largest class of submarine the Royal Navy has ever built. Sentinel was among the last of that production line, and being one of sixty-two is part of why so little was ever written about any individual one of them in peacetime.

The Captain Who Had Just Come From Singapore

Her first commanding officer is the most interesting thing about her, and he is not mentioned at all. Acting Lieutenant Commander Guy Stewart Chetwode Clarabut, DSO, took Sentinel when she commissioned, and he arrived almost directly from the other extreme of the submarine war.

Clarabut had been commanding HMS Stygian, and in July 1945 Stygian towed the midget submarine XE-3 across the South China Sea to Singapore, where she got into the Johore Strait and put charges under the Japanese heavy cruiser Takao. That operation produced two Victoria Crosses, one to XE-3's captain Ian Fraser and one to his diver, Leading Seaman James Magennis, and it is told properly in Stygian's own account rather than here.

The arithmetic is what stays with you. Stygian paid off at Portsmouth on 13 November 1945. Sentinel commissioned on 28 December. Six weeks separate a man handing over a boat that had towed a midget submarine into an enemy naval base from the same man taking command of a brand new submarine that had nowhere on earth to go. He was relieved the following year by Lieutenant Paul Murray-Jones, and after that the record simply stops telling us who had her.

A Quiet Peacetime Service

Sentinel's peacetime career is only thinly documented, though she is reported to have taken part in the Coronation Fleet Review at Spithead in 1953, and a family recollection preserved by former crew members describes a rather more personal moment, a crewman's son being christened aboard the submarine at Grand Harbour, Malta, in 1954, suggesting a period of Mediterranean deployment around that time.

Beyond these two glimpses, detailed records of her squadron assignments and exercises through the 1950s have proven difficult to trace.

That is worth explaining rather than apologising for, because there is a reason and it is not carelessness. A submarine at war generated paperwork by obligation. Every patrol ended with a written report from the commanding officer, describing what was seen, what was attacked, what went wrong and what the enemy did, and those reports went up the chain, were analysed, were filed, and survive today in the National Archives in enormous quantity.

A submarine at peace generated almost none of it. Exercises produced signal traffic and routine returns that nobody thought worth keeping, ship's logs were retained selectively and a great many were destroyed in later weeding, and there was no equivalent of the patrol report at all. The result is a genuine oddity of naval history: a boat that fought for six months is far better documented than one that served for sixteen years.

The review at least can be pictured, because it was enormous and it was photographed from every angle. On 15 June 1953 the new Queen reviewed 197 British warships at Spithead, with thirteen more from the Commonwealth, sixteen foreign warships and representatives of the merchant and fishing fleets anchored in lines off Portsmouth, and three hundred Fleet Air Arm aircraft flew past afterwards. Nearly two hundred British warships is a fleet that no longer exists in any form, and Sentinel was one small dark shape in one of those lines.

So the two glimpses above are not the whole of her career, they are simply the parts that happened to be written down by somebody outside the Navy. A fleet review is photographed and reported in the newspapers. A christening in Grand Harbour survives because a family kept it. The other fifteen and a half years, which were real and were spent by real crews, went unrecorded because nothing in them was unusual enough to write down.

Scrapped, Not Sold Abroad

It is worth correcting a suggestion sometimes made about this submarine, that she was sold on to the Danish Navy. No evidence for any such transfer survives in the record, and Denmark's genuine postwar submarine acquisitions from Britain were older U-class boats rather than S-class vessels like Sentinel.

The three Danish boats can be named, which puts the matter beyond argument. Denmark leased Springeren, Storen and Saelen from Britain from 1946, ran them for something like a decade while rebuilding a navy that had scuttled most of itself in 1943, and returned them in the mid-1950s. All three were U-class. Sentinel was never transferred to anybody and was still on the British list on the day she was sold for scrap.

She was instead sold for scrap in February 1962 and broken up at Gillingham in Kent, a quiet and unremarkable end befitting a submarine whose entire career, in truth, had been rather quiet and unremarkable from the very start.

It is worth resisting that verdict slightly, or at least qualifying it. Unremarkable is not the same as useless. A submarine in the 1950s Royal Navy spent her life being hunted on purpose: going to sea, diving, and letting frigates and aircraft practise finding her, over and over, so that the men who would have to do it for real knew how. Every escort crew that worked up in those years learned on a boat like this one.

It was not safe work either, whatever the word peacetime suggests. HMS Sidon was destroyed by one of her own torpedoes alongside at Portland in 1955, with thirteen dead, and she was doing nothing more dangerous than lying in harbour. Sixteen years of diving and surfacing in home waters without incident is not nothing; it is simply the sort of achievement that leaves no documents behind.