The Northampton Arm, a 4.75-mile branch of the Grand Union Canal, features a total of 17 locks to overcome a 107-foot height difference between Gayton Junction and the River Nene. Among these is Lock Number 4, situated within the Rothersthorpe Flight, a concentrated group of 13 locks near the Arm's start. This Grade II listed structure, built around 1815 and restored in the 19th and 20th centuries, showcases red and blue brick construction with metal swing gates and an overflow channel.
Beyond Bridge 4, boaters encounter a view of the M1 Motorway bridge and the distinctive Express Lifts tower in the distance. The Arm itself, opened in 1815, played a crucial role in transporting goods to and from Northampton and today provides both a scenic journey and a connection to the River Nene for leisure boaters.