The second Naval fort to be completed, was named and commissioned H.M.Fort "Sunk Head Tower" on the Ist May 1912. She was not placed into position 51.46.51N 1.30.21E until June Ist 1942.
The third Naval fort completed, was named and commissioned H.M.Fort "Tongue Sands" on the 17th June 1942. She was placed in position 51.29.55N 1.22.1 IE on the 27th June 1932.The final Naval fort to be built, for reasons unknown the Admiralty reduced the number of forts required from five to four, was named and commissioned H.M.Fort "Knock John" on the 16th July 1942 and sunk in position 51.33.72N 1.09.82E on
August Ist 1942

The cost to the Government of each Naval Fort, excluding armament and other military equipment was 3,040,000 at 1994 prices.With the completion of the four Naval forts in August l942, Holloway Brothers then set about the task of building a number of anti aircraft forts for the Army.  It had been decided by the Government that there was a need for anti aircraft defences in the Mersey and Thames estuaries to break up enemy bomber formations approaching targets from the seaward side and Mr G.A.Maunsell was asked to design a suitable solution.  

It was specified that each gun battery, and there were three required for the Mersey Estuary and three required for the Thames Estuary, should consist of four heavy and two light guns, centrally controlled, together with a searchlight position. The seperate guns were required to be spaced about 100 ft apart and it was obvious that the naval design whereby all the guns and equipment were mounted on one deck, would be totally unsuitable. It was therefore decided to use seven seperate towers and interconnect them with walkways above water.

Urgency dictated that the first three Army forts be positioned in Liverpool Bay, in the Mersey Estuary. Problems with the sea bottom there,which was known to be continually shifting, caused Maunsell to design a totally different type of foundation. After experiments he came up with the idea to make a foundation that would bury itself in the sand and having buried itself, would offer no obstruction to.the movement of the waves and currents above. The new design worked very well but not quite as the designer had anticipated. 

Because the new base was not self bouyant, a new procedure for floating the fort and depositing it in position was devised.. The procedure for the Mersey forts differing from that utilised by the Thames built forts. The Mersey Forts were of a slightly different design, they were taller than the Thames Forts, to take account of the deeper water in the Mersey estuary. They were built by the Cleveland Bridge and Engineering Company on a site at Bromborough. The completed forts were positioned in the Mersey Estuary during 1942.  The Thames Army Forts were commenced in August 1932 and the final tower completed in June 1943..

Construction of the Army forts was split into four sections:-

1)Construction of the fort base, consisted of four hollow reinforced concrete members, in the form of an Oxford picture frame, each member was 85 ft long, 6 ft high and J' 6" wide at the bottom and 5' 6" at the top. The floor, sides and roof were 5" thick. At the intersections of the four members, the'junction was concreted solid to provide a good anchorage for the four legs of the tower. The weight of each base was 300 tons.

2)The Legs and Superstructure. The hollow cylindrical reinforced concrete legs of the towers were 65 ft high, 3 ft external diameter and 2 ft internal diameter..  Each leg was pre-cast in three seperate sections, each weighing 5 tons and was about 17 ft long with the main 1.25" reinforcing bars protruding about 4 ft from each end. The junctions of the hollow leg sections were run in solid so that the leg had the structure of a male bamboo.. A concrete cap at the'top of the legs, 4 ft deep by 14 ft square with a 6 ft diameter hole in the centre, was cast in situ. Two 24" by 7.5" R.S.J.'s 43 ft long embedded in the concrete cap, formed the base for the steel superstructure. An octagonal steel house forming the superstructure of the tower contained three floors, bottom floor, intermediate floor and top deck. The width between the parallel walls was 36 ft and the walls were made from .25" steelplate. Each tower was specially designed to suit its equipment and the internal arrangements were very carefully planned so as to provide the accomodation for the whole fort regarded as one unit. Armoured parapets were provided around the top deck and around the magazine chambers.

3)Fitting out. Five of the seven towers forming each fort carried mooring facilities for ships, so that they could be resupplied under most conditions.

Steel framed windows, specially designed and built by Critall, incorporating black out shutters and louvres, provided plenty of daylight and ventilation.  Every tower had its own central heating installation and a boiler to supply hot fresh water. Each tower carried a proportion of the sleeping accommodation and recreational rooms for the 120 officers and men in a fort, and was also fitted with toilets, washrooms and bathrooms with hot and cold salt water laid on.

The walls of all living rooms were insulated with hardboard lining and all floors had a .75" thick covering of asphalt. The top deck floor was fully armour plated.  The Bofors tower was the headquarters for the men's messing arrangements and the officers' quarters and messing were on the central control tower.  The searchlight tower acted as the power station for the whole fort and was equipped with three 30 kw diesel powered electric generating sets. Electric hoists were provided to unload cargo.

he exterior of all the forts was given three coats of bituminous paint, the last coat being camouflage. The interior walls were painted pale green and cream.  Towers took about eight weeks to construct and were completed about two every two weeks. They were built at this pace since they could only be sited on high spring tides which occur once a fortnight.

he towers were
constructed in a definite order, the first tower to be sunk in any group had to be the Bofors tower, as it was able to defend itself until other towers arrived and it also contained the cooking and messing facilities for the crew. The other towers then had to follow in correct order to avoid difficulties in manoeuvring them into position.

4)Towing and Grounding

For the Thames estuary towers, two steel Thames lighters were modified by inserting an additional 20 ft section, giving them an overall length of 214 ft by 23 ft beam. The tower was suspended between the lighters by a complicated procedure, too lengthy to explain in this brief history, and towed down river to the chosen location before being winched onto the sea bed. The tow from Gravesend was usually undertaken by four tugs. Challenge, Crested Cock, Arcadia, Badia, Sun II and Sun III  are known to have been used . Each tower weighed 750 tons on average.
The total cost of providing the 21 towers making up the three Thames Army Forts but excluding armament and
military equipment ,was 21,000,000 at 1994 prices.

They were placed in theThames Estuary as follows:-Red Sands Army Fort placed at position 51.28;62N 0.59.60E Shivering Sands Army Fort placed in position 51.29.95N 1.04.48E The Nore Army Fort placed in position 51.25.45N 0.50.00E During their war service all the forts between them accounted for the destruction of about 22 enemy aircraft-and 30 V1 Flying bombs (Doodlebugs) In addition, the Naval Forts are credited with the destruction of one German "E" boat.


It was said after the war by Captain J.Hughes-Hallet that the true value of the Naval Forts was that they extended the radar coverage over the Thames Estuary. They provided accurate radar cover on the surface and at low heights, of a type not obtainable at that time with shore based sets. Since the most troublesome act by the German Luftwaffe was the laying of mines, they were able to plot with accuracy where they were being laid and thus make the necessary detours to avoid them. 

With the ceasing of hostilities the Army Forts were put on care and Maintenance and a special unit, the Anti Aircraft Fort Maintenance detachment, under the control of a Capt. A.B. Sandiford, took charge. During the "Cold War" period the forts were urgently re-equipped and brought to a state of readiness.  In 1952 new Radar equipment and revised models of searchlights were installed.  In 1953, the year of the great floods, The Nore Army Fort was partly flooded and lost some equipment which was washed away.. On March Ist 1953 a Swedish ship, the "Baalbeck" collided with the Nore Fort in thick fog and knocked over the Bofors tower and a 3.7" gun tower, killing four soldiers and resulting in the loss of a large amount of stores and equipment, including two Bofors guns and a 3.7" gun, plus a radar installation.

In 1956 the Army decided the forts could serve no further use and with the aid of an Admiralty crane from Chatham Dockyard, removed all of the heavy guns and equipment from the three forts.
In 1959 the Port of London Authority decided to remove the Nore hazard and began  to dismantle the Army Fort by removing the steel houses forming the superstructure and the interconnecting walkways. This work continued through 1960 when the legs were blown off and the bases uplifted and towed 17 miles to the foreshore at Alpha Wharf, Cliffe in Kent, where they still reside to this day and can be seen at low tide.

The Shivering Sands Army Fort also suffered damage during the 1950's when one of the towers was hit by shipping and destroyed and the connecting catwalk knocked away, seperating one tower from the others. The Port of London Authority installed automatic tide gauges to the legs of this isolated tower in 1964.  Reverting to the Naval forts, these were also put under care and maintenance immediately after the war, being serviced by the Thames Estuary Special Defence unit operated by the Navy from HMS Wildfire at Sheerness in Kent. Each fort had a crew of four maintenance men, who spent four weeks on and ten days off. They were resupplied by the MFV 1037, a Harwich based vessel attached to HMS Wildfire.

The Tongue Sands Fort and the Sunk Head Fort were to be utilised:by Trinity House to replace the pre-war light ships, but difficulties experienced in boarding and resupply during rough weather, caused them to have second thoughts.  During the period 1965 to 1967, at the height of the Pirate Radio era, at some time most forts were occupied with a view to using them for broadcasting. Red
Sands Fort was occupied by Radio 390, Shivering Sands Fort by Radio City and Knock John Fort was taken over by Roy Bates, a Southend, Essex entrepreneur.

Bates realising that Knock John was within the UK three mile limit and therefore UK jurisdiction, left and then took up residence in the Roughs Tower fort. One day whilst Bates was ashore replenishing his stocks, a rival, ex Radio Caroline operator Ronan O'Rahilly, with a group of men recruited from the pubs in Gravesend, occupied the Roughs Tower with the alleged intention of turning it into an offshore gambling club. They demolished the top decks leaving the deckhouse roof as a helicopter landing pad.
Over the next few months, occupancy changed frequently with Bates and O'Rahilly alternately taking up residence. Finally, a fight around the fort, involving the use of
firearms and home made petrol bombs, resulted in Bates taking possession. Bates proclaimed the Roughs Tower a principality and named it "SEALAND".

He had special postage stamps printed but unfortunately, the International Postal Union failed to recognise them. It is believed that Bates or his family, still occupy the Roughs Tower to this day.  The Sunk Head"Tower was occupied for a short time by a group calling themselves Radio Essex. Their stated intention was to operate a television station after normal BBC TV closed down at night but lack of capital delayed this plan.

One of the key operators was taken ill one night and had to be evacuated to a hospital urgently. Whilst they were ashore, a demolition team from the Royal Engineers, who had been on standby for weeks for just such an opportunity, bearded the fort and blew off the superstructure. Over the period of 18th to 21st August 1967, 24 Field Squadron, Royal Engineers, under the command of Major D. Ives, successfully demolished the Sunk Head Fort using some 3,200 Ibs of explosives, leaving just 20 feet of each tower showing above high water.  Over the years the action of the waves has caused scour around the pontoon base of the Knock John Tower with the result that the pontoon has broken its back and one of the twin towers has taken a distinct degree of tilt.

In 1993, the remaining 3.7" guns located on the Knock John Tower and the Tongue Sands Tower were removed by an RAF Chinook helicopter and taken to RAF Manston. Three of these guns were removed by road transport to a museum in the Orkneys and the fourth gun, the Tongue Sands "A" gun, the gun claimed to be responsible for the German "E" boat sinking, was taken to the Fort Gardens Gravesend, where it is currently on display awaiting refurbishment. A fitting resting place and the only reminder of the work carried out in the locality during
1942-43 involving the expenditure of  33,OOO,OOO

After the final Nore Army tower was placed in position on the 16thJune 1943, the Red Lion Wharf continued with war production, building reinforced concrete floating dry docks for use by the Allies in the Normandy Invasion. The designer of these huge concrete monsters was none other than Guy Maunsell. The yard closed with the ceasation of hostilities in 1945 and reverted to being a derelict site once again before being utilised for building the Northfleet Power Station in the 1960's.
Specification of the 3.7" gun.
A general service specification was issued in 1933 to Woolwich Arsenal and Vickers Armstrong. Of the two designs submitted by the parties in 1934, the Vickers Armstrong gun received the final approval. The intitial proof gun was ready by April 1936 and the first production gun delivered in January 1938. The gun was produced throughout the war years at around 200 guns per month.The weight of the gun and breach mechanism was 3930 Ibs. The total length was195.15", the length of the bore, 185". and the total weight of the gun ready for action was 23,100 Ibs. Traverse was 360 degrees and elevation, -5 degrees to plus80 degrees. The recoil of the gun was 18"

The HE shell fired by the 3.7" gun weighed 281bs and had a muzzle velocity of approx 2,600 ft per sec. Maximum range, horizontally was 20,600 yds and maximum ceiling when fired vertically, 41,000 ft. The rate of fire by hand was 10 rounds per minute and automatically, 25 rounds per minute. When mounted statically, as on the forts, the gun was known as a Mk2C.

The Bofors Anti-Aircraft Guns.

The weight of the gun and breach mechanism was 960 lbs and the total length 117.7". The length of bore was 88.58" and the weight of the gun ready for action was 4368 Ibs.. Traverse was 360 degrees and elevation minus 5 degrees to plus 90 degrees. The recoil of the gun was approximately 8 inches. The HE shell fired by the Bofors weighed 21bs and had a muzzle velocity of 2,700 feet per sec.  Maximum range, horizontally was 10,800 yds and maximum ceiling 23,600 ft.  The effective firing height as well as the effective range for aimed fire was 5,000 feet.. The rate of fire was 120 rounds per minute.