My new book, The Thames Estuary's Military Heritage was inspired by a period of time when I lived on the Isle of Grain, an extension to the Hoo Peninsula, a spit of land that juts out into the Thames Estuary, with Southend on the far side of the Thames. It is more than possible on a clear day to see from Grain the pier at Southend. My memories of those years of living on the Isle of Grain are vividly recalled whenever I fly into London’s city airport, a flight path along the Thames that provides excellent views of an area I know so well. And of one thing I learnt from living on the island, although admittedly no longer technically an island, was its important strategic position. For this reason, Grain acquired a massive number of forts and batteries, these placed there to prevent an enemy incursion along the Thames to attack London and its military-industrial complex, or of entering the River Medway where a second military-industrial complex also once existed.

Various defence locations in and around the Isle of Grain. (The Thames Estuary's Military Heritage, Amberley Publishing)

Without doubt, the defences placed in and around the Thames Estuary, including those on the Isle of Grain, were absolutely vital for the defence of the nation. Should this area of water fall into enemy hands, then the entire country would soon tumble. It was the Estuary, by way of the Thames, that was the pathway into London, the capital, which needed defending at all costs. An enemy gaining entry into the Estuary would not only endanger the capital, but the vast number of ships that traded into London by way of the Thames. It is also an area of water possessing additional strategic value through being of vital importance to the Royal Navy. Close to the mouth of the Thames, and adjacent to its point of confluence with the River Medway and just off the Isle of Grain, is located the Nore, a key naval anchorage where newly commissioned warships once assembled. Here they took on crews and received final instructions before joining the active seagoing fleet. It was also at the Nore, in 1797, that the Navy witnessed mass mutiny, some discontented seamen at that time even threatening to take their ships to Revolutionary France.   

Within easy reach of the Nore, was once located four of the nation’s naval dockyards. These also needed defending: Chatham, Deptford, Sheerness and Woolwich. While Sheerness actually overlooked the Nore, Woolwich and Deptford were located nearer to London with Chatham approached by way of the River Medway. Equally as vulnerable to attack by an enemy entering the Estuary, were numerous merchant shipbuilding yards, the Royal Arsenal, a massive gunpowder store at Purfleet and gun testing ranges that overlooked the Estuary. Elsewhere, I have referred to this huge combination of military might as a multiplex, for every aspect of the nation’s military was once represented here.

Thames Estuary's
Deptford dockyard, part of the military-industrial multiplex that would be vulnerable to an enemy attack by way of the Thames Estuary. (The Thames Estuary's Military Heritage, Amberley Publishing)

Most narrowly defined, the Thames Estuary can be viewed as a line drawn from Shoeburyness on the Essex coast to Sheerness on the Kent coast, a distance of approximately five miles (8Km). For the purpose of my book, Thames Estuary Military Heritage, and which is an overall history of the defences of the estuary, I have focussed upon the Greater Thames Estuary, for it was the defences of this wıder area that ultimately took responsiblity for securing the narrower seaway ınto London. For this reason, I have defined the Greater Estuary as including all of the northern coastline of Kent, stretching as it does towards London together with the entire coastline of Essex as far north as Clacton.

Red Sands Sea Army Fort seen from Whitstable. This fort being one of the forts built to defend the Estuary during World War Two. (The Thames Estuary's Military Heritage, Amberley Publishing)

Part of the defences of the wider Estuary dating to the reign of Henry VIII were a series of coastal forts built between Sandown to the north and Walmer to the south, a total of seven fortified points linked by an earthwork barrier. These would help defend the movement of merchant shipping in and out of London, while helping control this area of coastline from an enemy intent upon entering the Thames. Similarly, some 400 years later, the Estuary would be defended by a series of sea forts armed with 3.7in Heavy Anti-Aircraft guns and 40mm Bofor guns for the purpose of combatting low-flying mine-laying aircraft and enemy torpedo craft (E-boats).

Thames Estuary's
The Gravesend shoreline. During the 17th and 18th centuries this area of water was key to the defence of London, guns placed here intended to work in unison with those on the opposite shore at Tilbury. (The Thames Estuary's Military Heritage, Amberley Publishing)

On entering the Estuary, the distance between the shoreline of Kent to the south and Essex to the north, appreciably narrows, with this determining where, over the years, defences should be built. Between Shoeburyness and Sheerness the width is 5 miles (8km) but at Gravesend it is reduced to 2,400ft (732m) and at Woolwich 1,472ft (448m). For this reason, the earliest of the defences, when the range of guns was limited to a mile or less, much effort was spent on fortifications on either side of Gravesend Reach, but as the range of guns increased, and by the middle years of the 19th century, new heavily armed forts were constructed along the length of the Hoo Peninsula, the Isle of Grain and the Isle of Sheppey, but with attention also given to the strengthening of Gravesend and Tilbury should an enemy breakthrough still occur.

Philip MacDougall's book The Thames Estuary's Military Heritage is available for purchase now.