A Secret Underground City
Updated 3 October 2026
The secret underground city at Corsham tells an extraordinary chapter of British history: former Bath stone workings adapted for wartime industry and, later, a government headquarters intended for use in a nuclear crisis.
From Bath stone to wartime use
The underground quarries grew alongside the demand for building stone and the arrival of the Great Western Railway. In the years before the Second World War, parts of the workings were converted into ammunition-storage facilities. Wartime activity also included an underground aircraft factory.
The Ministry of Defence’s illustrated history explains how these different uses developed. It is important to distinguish the wider quarry network from the later government bunker, rather than treating every underground chamber as one installation.
A secret underground city for Cold War government
In the 1950s, work created a potential relocation site for central government. Known as the Central Government War Headquarters and by codenames including Burlington, it was designed to support government operations below ground.
Historic England’s records describe accommodation for the Prime Minister, operations rooms, a telephone exchange and a radio studio. These practical spaces make the story especially striking: an emergency headquarters needed places to work, communicate and live, not simply shelter.
Messages below ground
Communication was central to the plan. Alongside telephone facilities and a radio studio, a Lamson pneumatic-tube system carried messages through the complex. These surviving elements are recorded separately in the National Heritage List for England.
Explore the history through official sources
The site was declassified in 2004. Declassification does not establish public visitor access, so this article makes no promise of entry or tours. Use the official records and illustrated booklet to discover the story.
- Ministry of Defence: Corsham Tunnels — A Brief History (PDF)
- Prime Minister’s rooms and operations rooms
- GPO telephone exchange
- Radio studio
- Lamson terminus and fan room
Discover Box above ground
Lorne House is a base for exploring the village and the surrounding area. Our Box walks guide points to public routes, while Hidden Box introduces more of the locality’s history.
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