Braunston Canal Tunnel was completed in 1796 for the Grand Junction Canal Company. It measures over a mile, 1,867 metres to be precise. There is no towpath within the tunnel so horses used to transit overground while the boats were legged through. As the Grand Junction was a wide canal, the tunnel is 4.8 metres (15.7 feet) wide and there is room for two-way traffic as two seven-foot-wide narrowboats can pass within.
The western portal (only) of the tunnel is listed Grade II, rather oddly listed as the ‘entrance’ to the tunnel.
In 1870 a trial was conducted using an endless wire rope driven by steam engine to haul boats through the tunnel. The trial didn’t work out and in 1871 a steam tug was brought in. The charge for towing boats through the tunnel was one and sixpence (7.5p) although cheaper for empty boats.
The Grand Junction Canal was absorbed by the Grand Union Canal Company and the tunnel is now maintained by the Canal and River Trust. The eastern end retains a slight S-bend, whether through construction miscalculation or subsequent ground movement is not clear.