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
Greywell Tunnel and so avoid the possibility of closure under the Railway and Canal Traffic Act 1888. Harmsworth, the last trader working on the canal, bought the canal in 1923, but only the lower section up to Woking was used. The tunnel was finally closed when part of the roof collapsed in 1932, after which the canal to the west, including Basingstoke Wharf, was sold. It was still possible for canoeists to get through the tunnel until the late 1950s, but the blockage is now total. The tunnel is of interest for its bat populations: it has more roosting bats than any