Blisworth Tunnel was the only section unfinished. This was despite the tunnel having been under construction for seven years: the gap was filled by a temporary horse-drawn tramway over the top of the hill, with goods being transported from boat to wagon and back again. The tramway, built in 1801, was Northamptonshire's first railway. In March 1805, the tunnel was finally opened and the rails were used to connect the main line of the canal to the River Nene until the branch canal to Northampton was constructed. Until the 1870s travel through the tunnel was only achieved by men lying on their
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