UK secret underground bases

[mi6spook]

Has anyone come across declassified material, infrastructure oddities, or historical references that hint at underground facilities beyond the well‑known sites?

[David64]

Has anyone come across declassified material, infrastructure oddities, or historical references that hint at underground facilities beyond the well‑known sites?

You're MI6. You know how this goes.

I could tell you, but then.....


All joking aside, you might try here.

https://www.subbrit.org.uk/

[BeTheGoddess]

Your MI6. You know how this goes.

I could tell you, but then.....


All joking aside, you might try here.

https://www.subbrit.org.uk/

Durham Castle.

[andy06shake]

Has anyone come across declassified material, infrastructure oddities, or historical references that hint at underground facilities beyond the well‑known sites?

A Google search produces.

Hope Cove RSG (Devon) – partially buried, coastal, now derelict
Shipton-on-Cherwell (Oxfordshire) – concealed within quarry terrain
Skendleby (Lincolnshire) – linked to RAF command infrastructure
Kingsway Tunnels (London) — WWII origin, later Cold War use; parts only fully disclosed decades later
Guardian exchanges — hardened, blast-resistant phone hubs; many still officially “unremarkable buildings” above ground
Chislehurst Caves (London)
Box Tunnel & Corsham Area (Wiltshire)
RAF Holmpton (Yorkshire)
Porton Down Subsurface Facilities (Wiltshire).

Think there are some not half-bad urban explorer vids on YouTube that cover some of the above underground installations.

[ARM1968]

You might want to do a deep dive on Asfordby mine. Just a little taster. It was never a mine.

[andy06shake]

You might want to do a deep dive on Asfordby mine. Just a little taster. It was never a mine.

Closed in 97, allegedly due to "geological problems."

Plagued by, among other things, intense water ingress, heavy pressure from overlying rock, and volcanic sills

What do you think is down there? 

The volcanic sills part seems interesting.

https://en.wikipedia.org/wiki/Asfordby_Colliery