November 1945: How Britain went on the offensive with magnetic mines

Unexploded sea mines remain a hazard in the waters around Britain but in November 1945 they were being hailed as a key weapon in the defeat of Hitler. What set the sea mines of the Second World War apart from their predecessors was the fact that they could be used offensively, and the magnetic mine played its part in taking the fight to enemy targets.

The UK’s first foray into magnetic mines came with the M Sinker during the First World War. As noted by our correspondent, work on the magnetic mine and torpedoes was hastened greatly by the realisation in 1935 that Britain had to rearm.

“Hand in hand with these developments went the investigations into the magnetic properties of ships which formed the groundwork for the system of conferring a high degree of immunity upon ships by ‘degaussing’ them,” the author said. “As a result of all the work upon development, we produced a very satisfactory and robust form of magnetic mine. In the development of our magnetic mine we had worked on the principle of using the horizontal component of a ship’s magnetism to actuate the firing mechanism. This component had been selected because it is the stronger of the two except immediately under and close to the bottom of a ship, and because it is, for the practical purposes of mine design, unaffected by the earth’s magnetic field.”