The Storm of War: A New History of the Second World War

by Andrew Roberts

One task of the U-boats was to place magnetic mines in the sea-lanes around the British Isles; this could also be done by parachute by low-flying Heinkel He-111s and by E-boats (motor torpedo boats) and destroyers. By the end of November these had sunk twenty-nine British ships, including the destroyer HMS Gipsy, and had also put the brand-new cruiser HMS Belfast out of action for three years. Through the immense bravery of bomb-disposal experts Lieutenant-Commanders R. C. Lewis and J. G. D. Ouvry, who removed the two detonators, one of which was ticking audibly, from a mine spotted in the Thames Estuary, the secrets of the steel-hull-activated device were discovered. Within a month, Admiralty scientists had discovered a way of counteracting the mines by fitting electric cables around ships’ hulls, to create a negative magnetic, or ‘degaussed’, field. Soon afterwards a means of blowing up the mines, using wooden-hulled trawlers towing buoyant electrical cables, was also invented.