HMS Trenchant (S91): Three Hundred and Thirty-Five Days at Sea

Constructed at Barrow

HMS Trenchant was built by Vickers Shipbuilding at Barrow-in-Furness, ordered on 22 March 1983, laid down on 28 October 1985 and launched on 3 November 1986, her launch ceremony attended by Vice Admiral Sir Arthur Hezlet, who had commanded the celebrated wartime submarine of the same name. She commissioned into Royal Navy service on 14 January 1989, based at HMNB Devonport.

Hezlet at that launch was not a piece of ceremonial decoration. On 8 June 1945 he had taken the wartime Trenchant into the northern entrance of the Banka Strait off Sumatra and fired a full salvo of eight torpedoes at the Japanese heavy cruiser Ashigara from four thousand yards, spreading them deliberately from ahead of the target to astern of her. Five hit. The cruiser was carrying sixteen hundred troops from Batavia to reinforce Singapore and only about four hundred of them survived, though most of her own crew of some eight hundred and fifty were picked up. It was the largest Japanese warship sunk by a British submarine in the war and it brought Hezlet a bar to his Distinguished Service Order and the American Legion of Merit. Forty-one years later he stood on a slipway at Barrow and watched the name go back into the water.

A Difficult Early Incident

In 1990, during a training exercise, nets from the fishing vessel Antares became snagged on Trenchant, resulting in the trawler's sinking and the tragic loss of four fishermen, an episode that underlined the risks submarines could pose to civilian vessels even without any hostile intent.

The Antares

It deserves the whole story. The Antares was a fifty-two-foot prawn trawler out of Carradale, working the deep water of the Firth of Clyde off the Isle of Arran with three other boats nearby. At about seventeen minutes past two on the morning of 22 November 1990, Trenchant, dived and having just completed a Submarine Command Course exercise, picked up a close sonar contact to starboard and turned to port to avoid it. In doing so she went into the trawler's gear. Antares was pulled over, dragged upside down along the surface and sank very quickly. Her four crew had no chance at all to get out.

They were James Russell, aged thirty-six, Stewart Campbell, twenty-nine, William Martindale, twenty-four, and Dugald John Campbell, who was twenty. The submarine did not know she had done it.

The Marine Accident Investigation Branch reported in 1994 and did not equivocate. The accident, it found, was caused by a partial breakdown in both the structure and the standards of watchkeeping aboard Trenchant, following the completion of the command course exercise. It also said, in terms, that no blame whatever attached to the crew of the Antares, who were going about their lawful business of commercial fishing. In June 1992 the submarine's duty commander had been court-martialled on six charges of negligence, found guilty on three and severely reprimanded: for failing to appreciate how close the trawler was, for allowing her to remain on a collision course without establishing her range, and for not knowing there was a second trawler there at all.

The report made eight recommendations, broadly matching those of the Royal Navy's own board of inquiry and the Sheriff Principal's determination after the Fatal Accident Inquiry, and out of them came a formal code of practice governing how close a submarine may come to a fishing vessel: a set separation at periscope depth and a far greater one when dived. The uncomfortable truth is that the rules existed because of the Antares and not before her. Eight years earlier HMS Porpoise had towed an Irish trawler under in almost identical circumstances and all five of that crew had swum clear, and nothing had changed. The exercise Trenchant had just finished, incidentally, is the one described in HMS Oracle: the course that produces submarine captains.

Records and Firsts

Trenchant ran aground off the coast of Western Australia in 1997 but freed herself with minimal damage, and in 1998 tested non-hull-penetrating optronic mast technology.

The optronic mast is easy to skip past and was a genuinely large change. A traditional periscope is an optical tube that has to run down through the pressure hull to an eyepiece, which means a hole in the hull, a fixed position for the control room directly beneath it, and one officer with his eye to it. A non-hull-penetrating mast puts cameras and sensors on top of a stub that stops at the top of the fin and sends pictures down a cable, so the hull stays intact, the control room can go wherever the designer likes, and everybody in it can see the same image at once. Every British submarine designed since has been built that way, and Trenchant was one of the boats the idea was proved in.

In 2007 she became the first Royal Navy vessel to fire the new Block IV Tomahawk cruise missile in a live-firing trial in the Gulf of Mexico, and in 2013 she completed the longest deployment ever carried out by a Royal Navy nuclear submarine, an extraordinary 335 days at sea covering 38,800 nautical miles. She also took part in the Arctic ice exercise ICEX 2018.

The 2013 patrol is the one worth dwelling on. Three hundred and thirty-five days at sea and thirty-eight thousand eight hundred nautical miles is the better part of eleven months away and nearly twice round the world, and it remains the longest patrol any Royal Navy nuclear submarine has done. For the crew that means eleven months of artificial light, no weather, no daylight, no privacy and no news that has not been vetted, in a space where a man cannot walk more than about three hundred feet in a straight line. The reactor is indifferent. People are not, and records of this kind are set by ship's companies rather than by submarines.

ICEX in 2018 was a different kind of hard. The exercise takes submarines under the Arctic ice cap to work with an American ice camp, which means finding a lead or a thin patch and coming up vertically through several feet of ice without damaging the fin, the masts or the rudder, and doing it in water where a mistake cannot be corrected by surfacing, because there is a ceiling. Trenchant came out of a long refit shortly before it wearing the dark blue paint scheme that HMS Torbay had trialled a decade earlier, so the photographs of her in the ice show a submarine that is, unusually, not black.

The End of Her Service

Following the 2020 Integrated Review, Trenchant left active service in 2021 and was formally decommissioned on 20 May 2022 in a joint ceremony with her sister HMS Talent, in the presence of the Princess Royal, closing out a career defined as much by sheer endurance at sea as by any single dramatic operation.

Sharing a decommissioning ceremony is unusual and says something about the state of the fleet: two Trafalgars went out of the door together on the same afternoon because the Integrated Review had decided the Navy would run seven attack submarines rather than the number it then had, and the oldest hulls went first. Only HMS Triumph was left of the class after HMS Talent and Trenchant, and she lasted three more years. Thirty-three years of service, one record nobody has beaten, and one night off Arran that the Royal Navy has never been allowed to forget.