The Swift Ditch, a quiet unnavigable stream that by-passes Abingdon and creates Andersey Island - named after St. Andrew's church which once stood on it. At the end of Culham Reach, the Swift Ditch re-enters the River on the right, under a picturesque wooden footbridge, having left it about a mile upstream of Abingdon Lock. There is conjecture that the Swift Ditch was once the original course of the River but it is now thought more likely that it is the channel dug across the Abbey Meadow by Abbot Ordric in 1052 to improve the course of the River through Abingdon. It is known however, that the Swift Ditch was the main navigable channel from around 1060 to 1550 and again from 1630 to 1790 when the current lock at Abingdon was first built. The remains of one of the first pound locks built on the Thames in c.1635 can still be seen near the top of the Swift Ditch.

(This was passed to me from an unknown source so I am unable to credit it or link to the original site at present)