The tunnel has no tow path inside, but is wide enough for two narrowboats to pass in opposite directions.

[1] By the time the rest of the Grand Junction Canal had opened between London and Braunston, Northamptonshire in 1800, apart from the crossing of the River Great Ouse, the section of canal from Blisworth to the lower end of Stoke Bruerne locks 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.

Until the 1870s travel through the tunnel was only achieved by men lying on their backs pushing the boats with their feet (legging).

There was major rebuilding of the tunnel in the 1980s, with sections lined with pre-cast concrete rings.