Volume Twelve - Pre-Victorian to the Present Day - further aspects - A History of Penarth Dock by Roy Thorne . . .

The grab dredgers "Graball" and "Mudeford" were used to lay an Admiralty Testing Range off Lavernock Point. This range was set up to test equipment to counteract magnetic mines. The dredgers also laid electric cables from the range to the recording base on the shore near the point.

During the air raids between 1941 and 1942 a vessel was blown up by a mine at the entrance to the Ely Harbour, and the damaged vessel was not completely removed and the entrance cleared until nine months later. This affected coal exports from the Ely Harbour during 1941 : -

The German U-boats were causing havoc at the end of 1941 and beginning of 1942. The 45,000 ton battleship "Tirpitz" was the new pride of the German Navy and if that ship was to operate in the Atlantic then our vital supply line across the Atlantic would be cut.

On 15th January the "Tirpitz" arrived at Trondheim in Norway where she was a threat to Allied convoys carrying supplies to Russia. The greater threat was that this formidable ship should move to St. Nazaire on the jutting coastline of the Loire where the great dry dock built for the French liner "Normandie" was positioned, and from there easily threaten and perhaps devastate our convoys.