Admiralty M-N Scheme - Wikipedia
The Admiralty M-N Scheme' (sometimes given as "Project M-N") was a World War I British plan to close the Strait of Dover in the English Channel to German U-boats, by means of a chain of either eight or twelve massive towers linked by anti-submarine booms and nets. Only two towers had been constructed before the Armistice with Germany caused the cancellation of the project.
Does anyone have more information on this saying how long it was expected to take to complete?