Admiralty M-N Scheme

Attention turned to the Strait of Dover, which was used by U-boats based in Bruges in occupied Belgium, to gain fast access to the Atlantic trade routes and the busy Western Approaches.

The Engineer-in-Chief to the Admiralty, Sir Alexander Gibb, devised a scheme of eight or twelve large concrete and steel towers, placed at intervals on the sea bed across the Dover Strait from Folkestone to Cap Gris Nez.

Gibb had worked with T G Menzies and Colonel William McLellan on a submarine detection system based on a galvanometer, which was also to be incorporated.

[5] The Number One tower soon found an alternative use as a replacement for the Nab Rock lightship, 40 miles away off Bembridge in the Isle of Wight.

On 12 September 1920, it was towed out of Shoreham harbour by five Admiralty tugs, watched by a crowd of thousands and was sunk on a sand spit next to the rock on the following day.