HMS Isis (M2010): A Wooden-Hulled Minehunter Built to Fool the Mines

Built to Be Invisible to Mines

HMS Isis was one of eleven Ley-class inshore minehunters built for the Royal Navy during the mid-1950s, a particularly specialist little class built using composite construction, wood and non-ferrous metals rather than conventional steel, specifically to minimise the ship's own magnetic signature.

The reason anybody built eleven of these things is worth recovering, because the panic behind them was entirely genuine. In the autumn of 1939 the Germans began dropping magnetic mines into British estuaries from aircraft, and for several weeks they came close to closing the Thames. The mine did not have to touch anything; it lay on the bottom and waited for the magnetic field of a steel hull to pass overhead. Nobody in Britain had a counter to it until a German mine was recovered intact from the mud at Shoeburyness in November 1939 and taken apart by two officers who fully expected it to kill them. Ten years later the Soviet Union had inherited the entire German mine-development programme, the scientists who had built it and a very large stockpile, and British planners looking at a future war assumed that the first thing to happen would be the mining of every approach to every port in the country from submarines and aircraft. The Royal Navy accordingly ordered small mine countermeasures vessels by the hundred in the early 1950s. Isis was one of the smallest of them.

It was a deliberately unglamorous but notably clever piece of engineering: a magnetic mine designed to detonate when it detects a large steel hull passing overhead simply cannot be triggered by a boat built almost entirely without one.

She displaced a modest 164 tons fully laden, and shared the same basic hull design used for the Ham-class minesweeper and the Echo-class survey vessels, powered by twin Paxman diesel engines and armed with either a Bofors 40mm gun or an Oerlikon 20mm cannon.

That shared hull is a good illustration of how the programme was run. The Admiralty took one small wooden hull design of about a hundred feet and used it for three entirely different jobs: the Ham class as inshore minesweepers, the Ley class as inshore minehunters, and the Echo class as inshore survey craft, all built to essentially the same drawings by small yards and boatbuilders around the country who had never made a warship and did not need to. The naming was as tidy as the engineering. The Hams took the names of English villages ending in -ham and the Leys of villages ending in -ley, which is how a minehunter came to be called Cradley, and the larger Tons that did the same work in deeper water took the villages ending in -ton; the Ton class and what it was for are set out in the article on HMS Gavinton (M1140). Somewhere in the Admiralty in 1950 there was a man with a gazetteer and a very specific job.

A Different Kind of Minesweeping

HMS Isis and her Ley-class sisters were built for a distinct role compared to traditional minesweepers: rather than sweeping for moored or magnetic mines across a broad area, they were designed to locate individual mines and neutralise them directly in shallow inshore waters, painstaking, precise work carried out at close range in exactly the kind of confined coastal environment where larger vessels could not safely operate.

How you actually hunt a mine in eight feet of muddy water in 1955 is worth explaining, because the technology of the time was not up to much and the answer was mostly people. The high-definition sonar that eventually made minehunting practical did not exist yet, and a purpose-built coastal minehunter had been cancelled in 1953 for precisely that reason. What the Leys had instead was shallow water, and shallow water means divers. A ship would work a channel slowly, using what sonar and magnetometer equipment there was to find something worth a second look, anchor over it and put men down to see what it was and, if it was a mine, to deal with it by hand. In a British estuary that means diving in near-zero visibility, in a tide, on a soft bottom, on an object designed to explode. It is the same trade as bomb disposal with the additional problem of being unable to see your own hands, and it is done to this day by the Navy's clearance divers, whose casualty rate has historically been the highest of any branch.

A Working Life With a Thin Paper Trail

Detailed records of HMS Isis's early service are hard to come by, which is not unusual for a small, specialist vessel of a class that numbered only eleven ships in total; she did not even start out as Isis, launched on 24 February 1955 as HMS Cradley and only renamed Isis in 1963, by which point she had already spent the best part of a decade under a different name entirely.

Nobody appears to have written down why she stopped being Cradley, which is mildly irritating. The change in 1963 took her clean out of the class naming convention, and Isis is a classical name, borrowed from an Egyptian goddess, that the Royal Navy has used since the eighteenth century and that also happens to be the traditional name of the Thames along its stretch through Oxford. The likeliest explanation, given what happened to her afterwards, is that she was being moved out of the operational mine countermeasures fleet and into a training and reserve role and was given a name that suited it, which is a thing the Navy did fairly regularly. She was already eight years old, the class had never had a great deal to do, and by the 1960s the Tons had taken over most of the real work in deeper water. What she is not, on any account I can find, is a ship that was renamed for any dramatic reason at all.

By the mid-to-late 1970s she had settled into a rather more sociable second career, attached to the Royal Naval Reserve unit at HMS Wessex in Southampton and based at Vernon Creek within HMS Vernon, where she became the very first ship of her own belonging to the newly formed Southampton University Royal Naval Unit. One summer cruise under that arrangement took her considerably further afield than her usual coastal minehunting grounds ever had, up the River Seine to Paris, a properly unexpected destination for a vessel built to sniff out mines in shallow British waters rather than go sightseeing on the Continent.

The University Royal Naval Unit scheme she joined has turned out to be one of the Navy's better ideas and it is very little known. The first was set up at Aberdeen in 1967, with a Ham-class minesweeper as its training ship, and the model spread from there: a shore headquarters near a university, a handful of reserve officers, a small ship of the unit's own, and about fifty undergraduates who join for the length of their degree. They are made honorary midshipmen in the Royal Naval Reserve, they are paid for the time they do, and, crucially, they have no call-up liability and no obligation whatever to join the Navy afterwards. That last point is the whole design. The units are not a recruiting organisation, or not officially; they exist so that a proportion of each year's graduates, wherever they end up, have actually been to sea in a warship, stood a watch, taken a fix and learned what the Royal Navy is for. Some of them join. Rather more of them end up in Parliament, the Treasury, the civil service and the press, which over fifty years is arguably the more valuable outcome. Isis was Southampton's first ship, and a nineteen-year-old taking a wooden minehunter up the Seine to Paris is doing something that no amount of classroom instruction replaces.

She was sold to the Portsmouth ship-breakers Pounds in April 1982, her training role passing on to the purpose-built survey craft HMS Woodlark in 1986. What does survive of her story suggests she formed part of an important, if largely unheralded, corner of the Royal Navy's Cold War minesweeping capability, and that in her later years she quietly did just as much good introducing university students to naval life as she ever did hunting mines.

Pounds of Portsmouth, who bought her in 1982, deserve a footnote of their own. For decades the yard on the edge of the harbour was one of the strangest sights in southern England: a scrapyard full of complete warships, minesweepers, tugs, landing craft and at least one submarine, tied up or hauled out in rows, some of them being cut up and some of them being sold on to foreign navies or to film companies. It was where a very large proportion of the small ships of the postwar Royal Navy ended, and Isis went there in April 1982, in the same weeks that a task force was sailing for the South Atlantic. She had been a minehunter for eight years, a nameless training tender for a decade after that, and a student ship for the last few. There is no dramatic story in her, and that is more or less the point: the Royal Navy of the Cold War was mostly made of ships like this, doing quiet and specialised work that only matters when it suddenly matters a great deal, and then teaching the next lot how to do it.