We have set ourselves a goal of walking the Thames from source past the Thames Barrier (184 miles) and on to the River Darent (9 more miles). Most walkers stop at the Thames Barrier because the "Working River" is quite industrial as we now know! We even caught the bus from the Belvedere Industrial Centre back to the train.
The Thames Barrier is the 2nd largest movable flood control barrier (523 metres) in the world. It is closed in the event of a storm tidal surge combined with a high tide to protect the Thames upstream. This is why we can live happily on the Thames in Kew and not be concerned with flooding ("touch wood" as the Brits say).
As of 24th May 2008, we have walked from Staines to River Darent. The walk gets prettier and prettier as we walk upstream. Part of the adventure is finding our way to each starting point, a place to lunch, and our way home. And we get some exercise as a bonus!