Moving back from a brief taste of the broad beam of the Grand Union, little could throw into sharper relief the great strides in civil engineering that took place in the 50 years after 1770 than the difference in feel of the Oxford, especially the southern section to where I am bound, and the mighty Grand Union. The Oxford was authorised by Parliament in 1769, though not completed over its entire 77-mile length from its connection at Hawkesbury Junction with the Coventry Canal to the Isis Lock with the Thames at Oxford until 1790. The idea was to provide a water-borne link from the North-West and the Midlands with London, the last 100 miles of which would be on the Thames.

Initially, the James Brindley-surveyed canal did well, despite its curvaceous hugging of the lie of the land, and loathing of locks. But competition was around the corner in the shape of the Grand Union; built wide and straight, with a more direct route to London that slashed a week or more of the time from London to Birmingham. It quickly ate away at the Oxford's traffic, but not curiously at its revenues.

The secret lay in that the builders of the Grand Union agreed to share the route of the Oxford over a five-mile stretch between Braunston and Napton allowing the Oxford to charge outrageously high tolls for the privilege. This easily became the most expensive stretch of water on the entire canal system but the income allowed the Oxford to use the latest developments in engineering to considerably straighten the path of their canal, cutting 14 miles off the original 36 north of the Grand Union, where traffic had not been so deeply affected by the new route to the capital.

And so the company showed a healthy return well into the twentieth century. Now of course the canal has a new lease of life, particularly the meandering southern section through the prettiest of Oxfordshire countryside, with its lift bridges, and narrow locks, 39 of which gently lower the canal down to the Thames by the end of this coming week.

· Mike Holland is writing weekly online dispatches from his canal journey around England. Thanks to the wonders of wireless technology, you can email him at michael.holland4@btinternet.com.