Two very different UXO items found on Norfolk marshland

A suspected unexploded ordnance (UXO) item was recently discovered on the north Norfolk coast, prompting a callout from the Coast Guard. The item in question turned out to be a large Mark VI naval mine, which was found on Thornham Marsh, an area with a rich historical background related to military activity during both World Wars.

The Coast Guard quickly established a 500m exclusion zone around the device until the rising tide covered the area again. A Royal Navy explosive ordnance disposal (EOD) team was then deployed to handle the mine. Upon further inspection, the EOD team discovered a second item nearby – a wartime artillery shell. The shell was confirmed to have been fired but never exploded, posing a potential threat to anyone in the area.

Mark VI Naval Mine: a dangerous legacy from WWI

The Mark VI naval mine found on Thornham Marsh is a relic from World War I, a time when the British Royal Navy employed a range of defensive measures against German U-boats patrolling the North Sea. The Mark VI was a spherical, contact-type mine used to defend British waters against the threat of German submarines. It had an 86cm diameter and contained an explosive charge of 300lb (140kg) of Toxyl – a mixture of 60% TNX and 40% TNT.

These mines were part of the WWI defensive minefields laid in British waters to protect merchant vessels and naval assets. The Toxyl charge within these mines was powerful enough to sink a ship or cause severe damage to submerged vessels.

The Mark VI mines were tethered to an anchor, allowing them to float at a predetermined depth in the water. Once laid, these mines were designed to detonate upon contact with a ship or submarine. After the war, mine clearance operations involved severing the tether, which would allow the mine to float to the surface. These mines were often destroyed by rifle fire. However, many mines, like the one found in Norfolk, did not detonate and eventually sank to the seabed, where they remained until disturbed by tides or other environmental factors.

Although the Mark VI mines were not the largest deployed in British waters, their 140kg explosive charge still poses a significant risk. This makes mines like the Mark VI a dangerous reminder of the UXO (unexploded ordnance) threat in areas with historical naval activity.

Wartime artillery shell: traces of coastal defence

In addition to the Mark VI mine, the EOD team discovered a wartime artillery shell. The driving band at the base of the shell had distinct grooves, confirming that it had been fired but failed to explode on impact. This shell is believed to be a WWII 40mm anti-aircraft (AA) shell, commonly used by Light Anti-Aircraft (LAA) regiments for home defence during the war.

It is likely that this shell was fired out to sea from a coastal gun during the war and was carried by marine currents before eventually being deposited on the marshland. The coastal area near Thornham was historically used for coastal artillery and anti-aircraft batteries, further supporting the idea that the shell was fired as part of a coastal defence strategy.

The presence of both a naval mine and artillery shell in the same area highlights the dangers posed by UXO remnants from the wars, even many decades later. While smaller in size than the mine, the artillery shell still presents a significant risk if disturbed, as it may contain live explosives.

Historical military presence on the North Norfolk coast

The North Norfolk coast, particularly around Thornham, has a long history of military activity. During World War I and World War II, the area was home to a seaward coastal firing range and a network of anti-aircraft batteries. These defensive positions were put in place to defend against aerial and naval threats, with large numbers of artillery shells and mines being deployed in the region.

The presence of these UXO items today serves as a stark reminder of the intense military activity that took place along the coast during wartime. In the decades following the wars, many UXO items, including artillery shells, naval mines, and other ordnance, were left behind, either missed during clearance operations or buried beneath the surface.

The ongoing threat of UXO

The discovery of these two very different UXO items underscores the ongoing threat posed by unexploded ordnance, even in areas that may seem safe or far removed from the battlefields of the past. Whether on land, in marshes, or submerged underwater, UXOs are a constant hazard in certain regions, especially those with a history of heavy military activity.

At Brimstone UXO, we are dedicated to providing comprehensive UXO risk mitigation services to help identify, assess, and safely dispose of unexploded ordnance. Our services include UXO risk assessments, surveys, on-site support and clearance operations, which help ensure the safety of workers, residents, and communities in areas where UXO may still pose a risk.

Our expert team uses the latest technologies to detect and safely manage UXOs of all sizes and types. Whether you’re working on a development site, conducting archaeological research, or managing coastal or inland areas, we offer tailored solutions to meet your needs.

Brimstone UXO: safeguarding communities and projects

At Brimstone, we understand the complexities of dealing with unexploded ordnance, and we take a comprehensive approach to UXO risk management. With years of experience in the field, we offer a full range of services, including:

• UXO Risk Assessments: Identify potential UXO hazards and evaluate the risks associated with your site or project.
• UXO Surveys: Using cutting-edge technology to detect and locate unexploded ordnance.
• On-Site Support: Deploying EOD engineers to site to support ground intrusion activities.
• UXO Disposal: Safe and effective removal and disposal of UXO through controlled detonations or safe removal.
• Consultation and Advisory Services: Expert advice and guidance to ensure compliance with safety regulations and best practices.

If you’re unsure whether your project is at risk of encountering unexploded ordnance, contact our team today. We are committed to providing clear, professional, and timely UXO services, ensuring your project progresses safely and without incident.

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