With the outbreak of war in September 1939, the German Navy launched a massive mining campaign against British shipping using the magnetic influence mine.
The intention behind this was to blockade the supplies of materials to the Port of London. This new weapon was very successful and caught out the U.K.authorities. In the first 6 months of the war 150 ships were lost and over 200 lives.On a cold night in November 1939,a member of the 518 Coastal Artillery Regiment based at Shoeburyness saw a parachute descend and land on the mud at Shoeburyness. This turned out to be a magnetic influence mine. This proved an ideal chance to examine the mine, and create countermeasures.
It was necessary to pinpoint with accuracy just where the mines were being laid. The Royal Navy as a stop gap measure utilised the old Thames paddle steamers that had, pre-war, taken day trippers to Southend, Margate and Clacton from London. 40 mm Bofers guns were mounted on the stable platforms, and using gun crews from London, they cruised the Thames Estuary to deter enemy mine laying.
What was needed was a permanent base in the Estuary that could both deter mine laying and record the position of mines already laid. Commander Shankland, the Port of London Harbour Master for the Thames Estuary, through the Admiralty via Captain Hughes-Hallett R.N. requested Guy Maunsell to design a Fortress for use in the Thames Estuary. Before the war Guy Maunsell was responsible for the repair and overhaul of the Menai Straits Bridge, widening of Putney Bridge and building Storstrom Bridge in Denmark in 1934.In October 1940 Guy Maunsell designed marine Fort no.4, also known as "Thames Estuary Martello Tower” design.
Each Fort consisted of 5 parts.
The Reinforced Concrete Pontoon--2 in each Fort, each pontoon was 152 feet long,32 feet wide,20 feet deep.
The Pedestal--Single reinforced concrete structure straddling 2 pontoons, 8 feet high
The Towers--2 to each Fort. 2 drum like structures, each 24 feet in diameter and 1 foot thick. Height of each Tower was 60 feet, divided into 5 floors, fitted out for living accommodation,
Workshops or stores.
The Deck--Reinforced concrete slab surrounded by a parapet and deckhouse.
The Equipment--Comprising of 2 ammunition hoists, stairways, doors, lockers, bunks. 25k. diesel electric generating sets, bases to fix guns, radar aerials, searchlights.
H.M.Roughs Tower was de-gaussed at Tilbury prior to being towed down the Thames to be sunk 8 nautical miles off Harwich, Essex. During the tow down river, in most atrocious weather conditions, the Fort towering some 100 feet above water and weighing 4,500 tons, managed to collide with everything in its path, and the tugs had great difficulty in controlling it.
When in position, the Fort started to sink with a 30 degree tilt sideways and the 120 men on board had to hold on to whatever they could. At the crucial moment, the pontoon base hit
the sea bed and righted itself.
The Army Sea Forts were placed in the Thames as follows-
The Nore Army Sea Fort, midway between Sheerness and Shoeburyness.
The Red Sand Army Sea Fort, 6 miles off Minster, Isle of Sheppey.
Shivering Sands Army Sea Fort, 7 miles off Herne Bay, Kent.
The Naval Sea Forts were placed as follows-
H.M.Fort Roughs Tower--8 miles off Harwich, Essex.
H.M Fort Sunk Head Tower 12.5 miles off Harwich, Essex.
H.M Fort Tongue Sands 6 nautical miles off Margate, Kent.
H.M Fort Knock John 8.5 nautical miles off Foulness, Essex and 12.5 nautical miles off Herne Bay, Kent.
All Forts were abandoned in 1956, everything was left there, and Herne Bay people went out by boat to rob Knock John Fort.
During 1964, Radio Pirates occupied the Forts.
Since 1967 Television Companies have used the Forts for filming, such as "Dangerman" and an episode of "Lovejoy".
They served their purpose during the war years, and serve a useful role today, being used by the S.A.S. for oil rig simulated assault training.
Our Speaker Frank Turner was warmly applauded for giving a very good talk.