Blisworth Tunnel sections lined with pre-cast concrete rings. It was also used to test out the materials that were later used on the Channel Tunnel. An unused ring is on display near the south portal. Blisworth Tunnel Blisworth Tunnel is a canal tunnel on the Grand Union Canal in Northamptonshire, England, between the villages of Stoke Bruerne at the southern end and Blisworth at the northern end. The northern end is about from the northern end of the Grand Junction Canal at Braunston, Northamptonshire and the southern end about . At 3,076 yards (2,813m) long it is the third-longest navigable canal tunnel
Netherton Tunnel Branch Canal prior to construction. The main reason for the project being overbudget was the extra works necessitated by the condition of the ground through which the tunnel passes. In 1983, the British Waterways Board had of the brick invert replaced with concrete as a result of the invert rising sufficiently to impede navigation. In 2011, significant cracks were found in part of the tunnel lining. Traffic through the tunnel was limited, as a result. Repair work began early in 2013. The canal runs south-west from the BCN New Main Line at Dudley Port Junction and under the Old Main Line at