Blisworth Tunnel has no tow path inside, but is wide enough for two narrowboats to pass in opposite directions. Work began in 1793, but errors by contractor left a wiggle in the tunnel, and after three years work it collapsed due to quicksand, claiming the lives of 14 men. It was then decided to begin again with a new tunnel. 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
Chirk Tunnel was let in January 1796, and its construction was completed in 1801. The of canal eastwards to Frankton was opened immediately, because of the valuable trade in limestone from the Fron Quarries. The section through the tunnel, which also passed through Whitehouse Tunnel to reach Pontcysyllte was opened in June 1802. The tunnel is claimed to be the first in Britain to have a towpath running through it (along with its shorter neighbour - Whitehouse Tunnel). However, Berwick Tunnel on the Shrewsbury Canal was open by 1797 and included a towpath throughout its length. As the tunnel at Chirk is