Excelsior Tunnel: The Forgotten Site of Operation Orpheus

Inside the abandoned Excelsior Tunnel - the forgotten site of Operation Orpheus (Image: Nat; inside the abandoned Excelsior Tunnel)

The unassuming Excelsior Tunnel in Cornwall (also known as the Kit Hill Tunnel) is a place with two histories. One is very ordinary. The other is extraordinarily dark.

First, the regular history. First dug in about 1880, the Excelsior Tunnel was an attempt to connect to a nearby mine shaft, in the hopes of accessing a rich seam of tin believed to lie within the hill. Abandoned halfway, it was restarted again in the 1930s, only to – once again – remain unfinished. It was a story not untypical of Cornwall’s often-troubled mines, which were at times abandoned without ever really becoming profitable.

(Image: Nat)

However, what came next is about as far from typical as you’re likely to get. During the Cold War, Western and Soviet states alike became desperate for a means of tracking secret nuclear tests. For that reason, the Excelsior Tunnel was selected as the first site for experimenting with the detection of underground explosions, in a series of tests code named Operation Orpheus.

(Image: Nat)

Before any of our Cornish readers panic, there’s no evidence that a nuclear bomb was ever detonated beneath Kernow. Yet the tests that did take place were still mightily dramatic. In 1959, the UK Atomic Weapons Research Establishment detonated small charges in the granite of the tunnel, at depths of 100 ft to 300 ft.

(Image: Nat)

The resulting explosions rocked the earth, sending tremors out through the crust. Luckily, by the time the team was ready to detonate a 3,000 lb bomb, another site in Cumberland had been found and Cornwall was spared.

(Image: Nat)

Since the tests ended in 1960, the Excelsior Tunnel has remained abandoned. Yet it has never been filled in. This small space beneath the Cornish countryside endures as a reminder of days when the UK was working away in its bid to become a nuclear power.

(Image: Nat)

Related: 7 Giant Concrete Directional Arrows of Wartime Britain



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