Despite encountering quicksands in Braunston Tunnel, it was finished on 21 June 1796, and the canal opened to Weedon Bec, around 2.7 miles (4.3 km) to the south of the locks.

He proposed to build 29 locks to get beyond Blisworth, but was persuaded to try a different alignment by three engineers who were brought in to advise.

Low level headings were cut to drain the main workings of water, and the tunnel opened on 25 March 1805, the last part of the canal to be completed.

[3] The locks were built wide enough to take two narrow boats side by side, in the hope that the canals beyond the northern terminus could be persuaded to widen their locks and that wide barges carrying 70 tons could be operated.

Just below the junction, the railway line from London to Rugby crosses the canal and then runs parallel to it.

The Leicester section of the Grand Union Canal then turns off at Norton Junction, and the canal continues on the level, passing through Braunston Tunnel to reach the top lock of the six that descend to Braunston, 3.5 miles (5.6 km) from the top of the Whilton flight.

[8] Beside lock 9 is a cast iron milepost, dating from the same period, indicating that it is 5 miles (8 km) to Braunston, which is also listed.