See here for a more detailed writeup of this walk.
Starting at Ashby St. Ledgers, this route heads south past Welton, before meeting the Grand Union Canal. The next three miles of the walk are along the side of the canal, initially east to Norton Junction, and then north to Watford Locks, passing under the A5 and the West Coast mainline, and next to the M1 en route. This means the second half of the walk is not particularly quiet, with the continual rumble of traffic in the background, but it's not unpleasant, and watching narrowboats navigate the staircase of locks at Watford Locks is a good way to pass the time before the final section of the walk. Crossing over the A5, the last 'side' of the route heads back west to Ashby. The church at Ashby is well worth exploring, with remnants of medieval wall paintings and inscriptions that were uncovered after being whitewashed hundreds of years ago.