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Development of the Limpet Mine
In his book 'Winston Churchill's Toyshop', Stuart Macrae describes how he and Captain C.V. Clarke, M.C. developed the first limpet mine in Bedford. It began in June 1939 when Clarke received a telephone call from the War Office from Major M.R. Jeffris. At the time Macrae was editor of a journal called 'Armchair Science'; the journal had recently published an article about magnets which had caught the Major's attention.
As a result of this telephone call and subsequent meetings Macrae moved to Bedford and began work on the limpet mine. The raw materials for the first test devices - large tin bowls - were purchased from Woolworths and fashioned into containers for explosive by a local tinsmith. The next task was to devise a delayed action initiator which would cause the limpet mine to explode after a time delay of between half an hour to two hours. This was solved with the use of - quite incredibly - aniseed balls which took exactly the right length of time to dissolve. The mines were tested in the Bedford Swimming Pool.
The first few hundred limpet mines were made in Bedford but outside contractors were soon brought in. In all, over half a million limpet mines were made and issued for use.
Stuart Macrae went on to become second in command of MD1 (Ministry of Defence 1) a department charged with the task of devising special weapons for irregular warfare. This department was under direct control of the War Cabinet and by the end of the war had designed 26 entirely new weapons
Sources:
Development of the Limpet Mine by Bedfordshire Libraries, 2005
Page last updated: 22nd January 2014