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
Kennet and Avon Canal on a tunnel. The tunnel has red brick portals, capped with Bath stone, each with a decorative plaque of Pennant stone. The tunnel was begun in 1806 and finished in 1809. It is lined with English bond brickwork and has a wide bore to cope with the Newbury barges used on the canal. There is no towpath through the tunnel, so walkers and cyclists must walk across the top of the hill. When canal boats were pulled by horses the boatmen had to haul their barges through the tunnel by hand, pulling on chains that ran along the inside walls.