When the Queensway Tunnel was opened in 1934, it was quickly nicknamed the ‘eight wonder of the world’.
But for all of its engineering achievements and longevity, there remain a number of secrets lurking within the subterranean passageway.
Work began on the original ‘Birkenhead’ tunnel in 1925 and saw two teams begin to dig towards one another on opposing sides of the River Mersey.
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The project resulted in 1.2 million tons of rock being excavated from below the river - much of it being used to construct Otterspool Promenade in South Liverpool.
However the bid to build the underwater passage between Wirral and Liverpool was far from plain sailing.
Over 1,700 people worked on the construction of the tunnel, with 17 killed over the course of its nine year build.
Now new footage shows where the project came face to face with difficulties in the early phase resulting in a hidden stretch of tunnel that few will know about.
The video shows a short, hidden stretch that at one point was the original path of the Liverpool side of the Queensway tunnel.
However, in 1926, during the tunnel’s construction, workers excavating rock from the area hit a fault in the rock face.
To avert danger, the excavation teams were called back and set upon a new route below the riverbed of the Mersey.
Within the hidden tunnel there remain marks in the rock face caused by workers and their pickaxes.
There also remain holes in the walls where dynamite would have been planted to help blast a way through the dense layers of rock.
While a new, reliable route was found, the hidden tunnel provides a stark time capsule of the dangerous work that was required to build a route under the river almost 100 years ago.
When the tunnel was finally completed and opened in 1934, it had racked up costs of £8m - the equivalent to half a billion pounds today.
