Grand Junction Canal Nene at Northampton, to the turnpike road at Old Stratford (north-west of the modern Milton Keynes), and to Watford in Hertfordshire: those to Daventry and Watford were not built. The branch to Old Stratford was amended before it was built (see below). The branch to Northampton was delayed as the plans of the Leicestershire and Northamptonshire Union Canal to reach Northampton and thus join with the Grand Junction came to nothing. The link to Northampton was made by a tramroad transferred from Blisworth Tunnel, with the 5-mile (8-kilometre) canal from Gayton being opened in 1815. The link to Leicester was
William Jessop and the Pontcysyllte Aqueduct built by Thomas Telford. It is known as the Cosgrove aqueduct and was designed and built by Bevan. Two tunnels also had to be built, at Braunston and Blisworth. The Blisworth Tunnel caused great problems, and was unfinished when the rest of the canal was ready. In fact Jessop considered abandoning it and using locks to carry the canal over the ridge. Jessop's temporary solution was a railway line laid over the ridge to carry traffic until the tunnel was completed. The Grand Junction Canal was enormously important in encouraging trade between London and the Midlands.