HMS Gavinton (M1140): The Minesweeper That Found a New Soviet Mine in the Red Sea

The Build: Grimsby

HMS Gavinton was built by J. S. Doig at Grimsby, laid down on 29 September 1952 and taking 22 months to complete, finishing on 14 July 1954, a Ton-class minesweeper, one of the largest classes of minesweeper the Royal Navy ever operated.

J. S. Doig were not shipbuilders in the way that phrase usually implies, and the firm is worth a paragraph. It was founded in 1904 by John Salmond Doig, a Scottish boilermaker, at the Strathtay Iron Works on Grimsby's fish docks, and its first trade was making parts for and repairing the five hundred or so steam trawlers then working out of the port, which at that date was one of the busiest fishing harbours in the world. In the First World War the firm converted trawlers into minesweepers. In 1934 it bought the yard next door and began building tugs, trawlers and minesweepers of its own. In the Second World War it built wooden-hulled sweepers from scratch, and in the 1950s it built Tons, of which HMS Fiskerton was the last. The Ross Group bought the company in 1964 and the yard was closed during the 1970s.

Which is worth holding on to for what comes later. The ship that lifted an unknown Soviet mine off the bottom of the Red Sea in 1984 and handed British intelligence a weapon it had never seen before had been built thirty years earlier by a firm that no longer existed, on a fish dock in Lincolnshire, by men whose ordinary week's work was mending trawlers.

The Tons were the workhorses of the postwar Royal Navy in a way no other class managed. Something like 119 were built between 1951 and 1960, for Britain and for half a dozen other navies, with an aluminium frame planked in double mahogany and non-magnetic fittings throughout, so that a magnetic mine would not notice them; unusually for a coastal type, they had enough sea-keeping to make ocean passages under their own power, which is how Gavinton came to be in the Persian Gulf and later the Red Sea. And because they were cheap, roomy, shallow and available, they ended up doing almost everything: minesweeping and minehunting, fishery protection, anti-smuggling work, Royal Naval Reserve training, patrol duty in Hong Kong and Northern Ireland, and quietly putting people ashore in places nobody discussed. Why so many small sweepers were built and then laid up is explained in the article on HMS Flintham (M2628).

She did not actually enter service until 11 May 1956, initially serving as Senior Officer of the Vernon Training Squadron based at Portsmouth, a role centred on training rather than active minesweeping.

Training and Reserve

HMS Gavinton continued her training duties with the Vernon Squadron through to 1962, before being placed in operational reserve at Hythe between August 1962 and August 1966, a fairly typical fate for a good many Ton-class vessels built in numbers well beyond the Royal Navy's immediate peacetime operational needs during the quieter middle years of the Cold War.

The Persian Gulf

HMS Gavinton was recommissioned in October 1968 for the 9th Minesweeping Squadron based in Bahrain, and spent several years conducting patrols and exercises in the Persian Gulf region between May 1969 and October 1971, part of the Royal Navy's long-standing commitment to maintaining a presence in a region of genuine strategic importance to British interests.

Two things happened to her either side of that Gulf commission, and between them they explain how she came to make the discovery she did. The first is that between September 1966 and October 1968 she was at Chatham being converted from a minesweeper into a minehunter, which is not a refit so much as a change of trade. A sweeper tows gear through the water and hopes to cut a mooring wire or set a mine off at a safe distance. A hunter uses sonar to find individual objects lying on the bottom and then sends a diver, or later a remotely operated vehicle, to look at each one and deal with it. The first is a farming job. The second is closer to archaeology.

The second is that when she came home from Bahrain at the end of 1971 she went onto route surveys, which sounds like the least interesting duty in the fleet and is in fact the foundation of the entire business. A minehunting sonar shows objects on the seabed, and the seabed of any busy stretch of water is thick with them: wrecks, boulders, anchors, oil drums, chain, lost containers, a hundred and fifty years of dropped rubbish. If you do not already know what is down there, every single contact is a possible mine and has to be dived on, and that takes hours you would not have in a war. So minehunters spend years in peacetime quietly mapping the approaches to their own ports and building a catalogue of what is normal.

That is exactly the discipline that mattered off Suez in September 1984. A ship whose people had spent a decade learning to tell an ordinary seabed object from an unusual one was put over a shipping lane in forty-two metres of water and asked to find something that should not have been there, and she found it. The unglamorous years are not a gap in her record. They are the reason the interesting part worked.

Discovering a New Soviet Mine

Operation Harling existed at all because something rather alarming had been happening in the Gulf of Suez and the Bab-el-Mandeb strait that summer. Beginning on 9 July 1984, when the Soviet cargo ship Knud Jespersen reported an explosion beneath her hull, seventeen merchant vessels of wildly varying sizes suffered mysterious underwater blasts over the following weeks. A group calling itself Al Jihad claimed responsibility, alleging that some 190 mines had been sown across the southern Red Sea, and with Egypt's Suez Canal revenues and Saudi Arabia's Hajj pilgrimage traffic both under threat, Britain joined an international mine countermeasures force alongside the United States, France, Italy and the Netherlands.

HMS Gavinton's most historically significant moment came during that very deployment, between July and October 1984. On 12 September, she located a mine-like object lying in 42 metres of water on the edge of the southbound shipping lane leaving the Suez Canal. Royal Navy divers made it safe before it was recovered and examined, revealing a previously unknown type of Soviet multi-influence mine packed with some 720 kilograms of RDX-TNT explosive, subsequently designated Type 955, a properly valuable piece of Cold War intelligence work.

Recovering an entirely new class of enemy mine intact gave British and allied naval intelligence a direct look at Soviet mine technology that would otherwise have remained purely theoretical, exactly the kind of unglamorous but particularly consequential work that minesweepers performed throughout the Cold War, largely unnoticed by the wider public but of real value to naval planners.

The words multi-influence in that sentence are the important ones, and they explain why finding this particular object mattered so much. A simple mine fires when one thing happens: a ship touches it, or its magnetic field crosses a threshold. A multiple-influence mine samples several signatures at once, magnetic, acoustic and the pressure wave a hull pushes ahead of itself, and only fires when the combination matches what it has been told a warship looks like. It can also be given a ship counter, so that it ignores the first six or ten vessels over it and fires at the eleventh, and a delayed arming period, so that it lies inert for days or weeks after being laid. All of that is designed to defeat sweeping: a swept channel can be declared clear and then kill a ship the following week. It is the reason the Royal Navy moved from sweeping to hunting, finding and destroying each mine individually with sonar and a diver or a remote vehicle, which is the job described in the article on HMS Dovey (M2005).

And an intact example is worth an extraordinary amount, because everything else is inference. Without one, an intelligence assessment of a Soviet mine consists of what has been read in a manual, what has been deduced from the damage it does and what somebody has guessed. With one, the analysts at Portsmouth had the actual firing unit, the actual sensor package, the actual arming logic and 720 kilograms of explosive to weigh; they could work out precisely what signature set it off, and therefore precisely how to sweep it, how to make ships quieter and how to set the sonar to recognise its shape on the seabed. One object recovered from 42 metres of water off the Suez Canal answered questions that had been open for years.

Nobody was ever formally blamed for laying the things, though circumstantial evidence, including the suspicious movements of an Egyptian ferry called Ghat, pointed towards Libya, and the American State Department concluded there was "persuasive circumstantial evidence" of Libyan involvement. Whether the motive was to damage Egypt economically or simply to test newly acquired mines under real conditions remains, to this day, a matter of educated guesswork.

The most unsettling interpretation is also the most likely, and it is worth stating. If the object was to close the Red Sea, the campaign failed: seventeen ships were damaged and none was sunk, the Suez traffic kept moving and the pilgrim ships kept sailing. If the object was to find out how a modern multiple-influence mine performs against real merchant traffic in real conditions, in a place where nobody could prove who had done it, then it worked perfectly. Somebody laid a couple of hundred sophisticated weapons in an international waterway, watched what happened, and was never held to account for it, and one of the very few tangible results was a British minesweeper thirty years old lifting one of them off the bottom and handing it to naval intelligence.

The End

HMS Gavinton was paid off on 12 December 1986, after 26 years of full operational service, and was eventually broken up by Brugse Scheepssloperji in Belgium on 14 October 1991, closing out the career of a minesweeper whose quiet training and patrol duties had, in her final active years, produced a notably significant intelligence discovery in the Red Sea.