KNOCK JOHN MAUNSELL FORT: A WWII RELIC STILL STANDING
A UNIQUE PIECE OF WWII HISTORY: EXPLORING KNOCK JOHN MAUNSELL FORT
Have you ever wondered what it would be like to explore a WWII sea fort? Knock John Maunsell Fort, a historic sea fort in the Thames Estuary, was one of the highlights of our private boat trip with Brownes Thames Estuary Boat Trips. We couldn’t wait to see this iconic structure up close.
We set sail from Old Leigh in Leigh on Sea on a beautiful sunny late-October morning. The waters were unusually calm, and as we drew closer, Knock John Maunsell Fort emerged, dominating the horizon. Until you’re up close, you can’t truly appreciate its sheer size.
We circled the structure several times, appreciating every detail that remained. The weathered concrete, the rusting steel, and the remnants of its wartime purpose were all fascinating to behold. It was hard to imagine the fort in its heyday, a vital part of Britain’s defences, although historical photos help!
COMING SOON: Keep a look out for our blog of the full itinerary of the boat trip.
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The History of Knock John Maunsell Fort
Knock John, also known as HM Fort Knock John or “The Goalpost” by some, is a Maunsell Sea Fort located in the Thames Estuary. Built in 1942, it’s one of a series of imposing concrete structures that emerged from the water during World War II. These enigmatic giants, designed to protect London from air attacks, are a testament to human ingenuity and a reminder of a unique chapter in British history.
A Network of Concrete Forts
Emerging from the waters of the Thames Estuary, the four naval forts were Rough Sands, Sunk Head, Tongue Sands, and Knock John. They were constructed in dry dock and assembled as complete units before being towed off by tugs and deliberately sunk onto their sand bank positions in 1942.
A Concrete Colossus
Each fort was a marvel of engineering, comprising a reinforced concrete pontoon supporting twin cylindrical towers. These towering structures housed a complex network of rooms, providing accommodation, storage, and operational facilities for the fort’s crew. A steel framework extended from one end, supporting a landing jetty and crane for resupplies.
Facts about Knock John Maunsell Fort:
- Codename – Uncle Four (U4)
- Reinforced concrete pontoon measuring 168 by 88 feet
- Two hollow cylindrical towers – 24ft in diameter
- Gun deck and upper deck
- Central tower controlling radar equipment
- Tower legs divided into seven floors with accommodation and storage areas.
- Steel framework at one end to facilitate landing jetty and crane
Despite their imposing presence, during the Second World War, these four forts destroyed only one German torpedo boat.
Deep dive into Guy Maunsell’s WWII Designs
For a deeper dive into the engineering marvels of WWII, we recommend watching a short documentary by Frank R Turner. This film details the construction of a few of Guy Maunsell’s innovative designs.
A Unique History
After the war, the forts fell into disuse. Knock John was decommissioned in 1945 and abandoned in 1956. However, its history took an extraordinary turn in the 1960s when Paddy Roy Bates occupied the fort and established Radio Essex, later renamed BBMS (Britain’s Better Music Station). This bold move sparked a unique legal battle that resulted in Bates being forcibly evicted.
Undeterred, Bates turned his attention to Rough Sands, another Maunsell Sea Fort. He successfully occupied it and declared it the Principality of Sealand, a micronation that he claimed sovereignty over. Today, only Knock John and Rough Sands remain, with the latter serving as the de facto capital.
A Fascinating Relic
Today, Knock John remains a fascinating historical landmark and a reminder of a unique chapter in British history. It is a popular destination for history enthusiasts, offering a glimpse into the past and a testament to human ingenuity and ambition.
A Unique Thames Estuary Experience
Want to experience the Thames Estuary like never before? We recommend Brownes Thames Estuary Boat Trips for an unforgettable Thames Estuary experience! Their private boat trips are the perfect way to explore this historic waterway in style. Our skipper Angus was incredibly knowledgeable and passionate, sharing fascinating stories and insights along the way. We can’t wait to book another tour with Brownes!
REFERENCE LIST:
- Frontline Ulster (n.d) Sectional elevation plan [accessed October 2024]
- Frank R Turner (1995) The Maunsell Sea Forts [accessed October 2024]
- Offshore Radio Museum (1942) Knock John during & after grounding [accessed October 2024]
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