Have you seen what looks like a layby halfway through the Liverpool to Wallasey section of the tunnel? Here is why it is there.
Work started with construction by hand of an 8ft high pilot tunnel through sandstone under the River Mersey. It took about a year to complete. Then the giant laser-guided â€˜Mersey Moleâ€™ arrived to excavate the main tube. Having previously been deployed on the construction of Pakistanâ€™s vast Mangla Dam, the 35-tonne, 45-foot long machine carved a route under the River Mersey, leaving a concrete lined tunnel in its wake. However conditions were very different to Pakistan and water mixed with grit to cause the Mersey Mole to break down mid-river. Unable to move backwards or forwards, it led to a dramatic and difficult month-long operation to replace its main 10 tonne bearing.