The secret chemical weapons hidden in remote part of the UK | UK | Travel

Tucked away in a secluded Welsh valley lies the abandoned Rhydymwyn’s MS Valley Factory, a chemical weapons facility that played a pivotal role in the development of nuclear arms. Despite being long closed, it remains the most intact chemical weapons site in the UK and continues to be monitored as part of the international Chemical Weapons List.

The sprawling 86-acre site is now overgrown and encircled by decaying barbed wire. A labyrinth of ominous and historic wartime tunnels deep beneath the surface has been largely inaccessible since 1939. However, the former MS Valley Works on Nant Alyn Road, near Mold, hold national and international importance.

The site’s history dates back to 1939 when the Ministry of Supply (MS) purchased the land and transformed it into a chemical weapons factory and storage area. Over 100 buildings were constructed, interconnected by a railway network.

The River Alyn flowing through the site was channelled into canals and culverted, and by 1943, the complex employed 2,200 people.

Deep underground, an extensive network of rock-cut tunnels and bombproof caverns was carved out.

It was here that more than 3,000 tons of lethal mustard gas was stored, ready for use if the Nazis deployed chemical weapons.

Believed to be virtually undetectable from the air, the factory was the only facility of its kind not discovered by Nazi intelligence. Moreover, it was the work conducted at this remote site that sparked the nuclear revolution.

The survival of this ultra-secretive site can be largely attributed to its secluded location, nestled within a lengthy, wooded valley.

Now, the public is being granted the unique opportunity to explore this haunting facility, which was initially utilised in the battle against Nazi Germany and later played a pivotal role in nuclear weapons research.

Many might not realise the significant part this site played in the creation of nuclear weapons – a project codenamed Tube Alloys – which is likely to be its most enduring legacy. It evolved into a hub for gaseous diffusion research, providing fissile material, with an impressive roster of 10 Nobel Laureates contributing their expertise at one point.

Several scientists who were stationed at the North Wales site subsequently contributed to the Manhattan Project, the clandestine US government initiative during World War Two aimed at developing nuclear weaponry, culminating in the atomic bombings of Hiroshima and Nagasaki. 

Physicist J. Robert Oppenheimer, whose story is depicted in the blockbuster film ‘Oppenheimer’, spearheaded the laboratory that engineered these catastrophic bombs.

However, one historical expert asserts: « Without Rhydymwyn, Oppenheimer would never have been able to develop the Atomic Bomb. »

Post-war, the facility became obsolete in the 1950s when Britain abandoned its chemical weapons capabilities. It was then repurposed as a major storage site for emergency provisions and raw materials in anticipation of a nuclear war, intended for distribution via mobile bakeries and canteens.

Highly confidential proposals were once made to transfer a staggering 4,700 tons of gold from the Bank of England vault located at Mount Pleasant in case war erupted anew.

The MS Valley Factory, which operated until 1994, underwent extensive works nine years later, leading to the demolition of several wartime structures.

The site is now an exclusive nature reserve with limited access. After devolution, the complex was offered to the fledgling Welsh Government by the UK Government, complete with a « dowry » payment, yet concerns over potential remnants of chemical warfare dissuaded them from taking it on.

Maintaining the site isn’t cheap; as of 2010, the annual costs for security, upkeep, and inspections hovered around £1 million. Meanwhile, speculation swirled about what might remain hidden within the sealed tunnels.

Clarity regarding the complete removal of chemicals came in 2006, when an independent expert confirmed their absence. Despite this, the site retained an aura of history: in 2014, an urban explorer infiltrated the area, unearthing a trove of forgotten items including a cabinet filled with documents outlining the premises and a worker’s coat pocket containing a package of cigarettes.

Rosina Parry, the last known survivor who worked there during the war and was 21 in 1941, recounted her experiences in a 2012 television interview.

Her duty was to ensure that mustard gas bombs were not compromised, although at the time, nobody openly referred to the mustard gas despite rampant rumours.

A woman opened up to S4C about her experience at a secret wartime facility: « If ever you got little spots on you, if there was a leak, it used to burn you.

We always had our gas-masks, we didn’t go anywhere without our gas-masks! Nobody knew what was going on there really. Nobody knew what I was doing there from where I lived (in Greenfield, Holywell). »

The enigmatic abandoned site now offers rare public tours that quickly become the talk of the town. The Rhydymwyn Valley History Society is preparing for an upcoming tour on Sunday, April 27, which caused quite a stir as nearly 3,000 people clamoured for just 60 available spots.

Due to overwhelming interest, the society expanded its tour list to accommodate 96 fortunate individuals, each shelling out £10. An additional tour is under consideration for Sunday, June 22, awaiting a nod from the UK ministry Defra.

Should approval be granted, the society plans to open applications for these sought-after slots on their website and Facebook page, with an emphasis on first come, first serve allocation.

Colin Barber, the chairman of the society, attributes much of the intrigue surrounding this location to its significant contributions towards the development of nuclear weapons, known by the codename Tube Alloys.

« It became a centre of excellence for research into gaseous diffusion to provide fissile material. At one point, 10 Nobel Laureates were working there and in the wider area over to Widnes. After the war, a gaseous diffusion factory was established at Capenhurst in Cheshire for uranium enrichment.

« At Valley, the work was carried out at the P6 building for the Tube Alloys project before this was moved to the States, later developing into the Manhattan Project. P6 is still standing and, as well as opening the tunnels to the public, we want the building’s importance to be properly recognised. »

Should spots open up for the June 22 tours, they can be booked through the Rhydymwyn Valley History Society website here. Prospective visitors need to fill out a form and pay a £10 fee.

The tours are not open to those under 16 or pregnant women, and likewise, pets and drones are prohibited. There is parking available at the venue. Additional tours could be planned later in the year if there’s enough interest.