HMS Mastiff (T10): Lost Trying to Recover the Very Mine That Would Destroy Her

Constructed at Leith for an Unglamorous but Essential Job

HMS Mastiff was ordered on 27 January 1937 from Henry Robb Ltd at Leith, launched on 17 February 1938 and entered service on 16 May 1938, a Dog-class anti-submarine trawler, one of a family of small, sturdy vessels adapted from the design of ordinary commercial fishing trawlers to serve in the decidedly less peaceful role of coastal patrol, minesweeping and anti-submarine work.

She displaced 520 tons, measured 150 feet overall with a 27-foot-6-inch beam, and was the second of the Dog-class trawlers Henry Robb built for the Admiralty, unglamorous figures for an unglamorous but essential job: the close-inshore, dangerous work that larger fleet units simply could not spare the time or the draught for.

Guarding the Coast Under Lieutenant Commander Ouvry

HMS Mastiff served from August 1939, on the very eve of war, under the command of Lieutenant Commander Aymé Arthur Carrington Ouvry, taking on the kind of steady coastal and anti-submarine patrol duties that so many small trawlers of her type carried out largely unremarked in the opening months of the conflict, work that mattered enormously to the safety of Britain's coastal waters even if it rarely made headlines.

Destroyed Hauling In the Very Threat She Was Meant to Clear

HMS Mastiff met a properly cruel end on 20 November 1939, while engaged in mine recovery operations off the British coast.

She was attempting to haul aboard a mine that had broken loose from a German minefield laid only days before, sunk one nautical mile off the Tongue Lightship in the outer Thames Estuary. There would have been little point risking a boarding party on an ordinary contact mine, so this was almost certainly one of the new German magnetic mines that had begun sinking ships around the coast with no obvious cause, and of which the Admiralty desperately needed an intact example to study. The mine detonated as it was being hauled aboard, destroying the trawler outright.

Five of her crew were left missing and presumed dead, one further man died of his wounds, and nine more were wounded in the blast, a heavy toll for a vessel barely eighteen months into her service, and one of the earliest reminders of just how lethal the unglamorous business of mine warfare could be, right from the opening weeks of the war. Survivors were pulled from the water by the trawler HMT Cape Spartel and the Margate lifeboat.

It is worth knowing what kind of month she died in. By late November 1939 four or five merchant ships a day were going to the bottom around the British coast, from a weapon that left no wake, needed no contact and could not be swept by anything the Royal Navy owned. The Port of London was barely being kept open. Nobody in the country had yet seen inside one of these mines, which is why six men were sent to lift a live one out of the sea by hand, and why the Admiralty thought that was a reasonable thing to ask.

Consider what they were doing it in. Mastiff was 520 tons and twelve knots, with one 4-inch gun forward, two .303 machine guns and about thirty-five men aboard, a fishing boat with a naval ensign. She was the Royal Navy's first minesweeper casualty of the war. The following day the brand-new cruiser HMS Belfast, ten thousand tons of her, had her back broken by the same kind of weapon in the Firth of Forth and spent the next three years in dockyard hands. The mine did not much care what it was hitting.

Two Officers Named Ouvry

Lieutenant Commander Ouvry himself was blown clear into the water when his ship went up, a miraculous escape his own son later described in family recollections of the disaster, and he survived to take command of the destroyer HMS Westminster that December. He would go on to win the DSC in October 1941, after Westminster helped sink two German E-boats defending Convoy FN.31 off the Norfolk coast, an action that earned her the nickname "E-boat Killer No 1".

There is one further, genuinely remarkable coincidence buried in Mastiff's story. Just three days after she went down trying to recover an intact magnetic mine, her captain's own first cousin, Lieutenant Commander John Ouvry of HMS Vernon, succeeded where Mastiff's crew had died trying: on 23 November 1939 he and Chief Petty Officer Charles Baldwin waded out onto the Shoeburyness mudflats and, using tools specially made from non-magnetic materials, became the first men to safely defuse one of the new German magnetic mines. The intact fuze they recovered went straight to the physicist Alfred Wood, whose dismantling of it the following day set in motion the degaussing countermeasures that would protect Allied shipping for the rest of the war, a breakthrough bought, in part, by the six men Mastiff lost trying to do the very same job a few miles up the coast.

The two Ouvrys were not a coincidence of surnames. They were first cousins, and the surname is unusual for a good reason: the family were Huguenots, silk weavers who came over from France in about 1683 and became one of the biggest houses in the London trade. Both cousins were lieutenant commanders in November 1939, both were in the mine business, and they were regularly mistaken for one another.

Which produced one of the stranger moments of the war. When John's DSO for Shoeburyness was gazetted, Arthur's friends read the notice, saw the rank and the name, and congratulated him on it. He had been blown into the Thames Estuary by the same class of weapon three days before his cousin took one apart with a set of non-magnetic tools.