The controversial 3/4 mile stretch of river, known as Hedsor Water, was part of the main channel of the Thames until it was later bypassed by Cookham Lock. For more than a century it has been claimed as private water by successive riverside landowners, who have prevented public access to it.

The High Court ruling says that the disputed waterway is, in fact, a public right of navigation with open access to all boaters.

Commenting on the agency's victory, Eileen McKeever, Thames Waterway Manager, said: "The agency is the champion of open access for all to the non-tidal Thames. We have fought very hard to ensure this lovely backwater is reopened to the public."

The claimant, Josie Rowland, has indicated she wishes to pursue an appeal against the decision. And until the appeal position has been clarified, the Environment Agency will not be taking any action to remove the signs or obstructions in Hedsor Water.

A survey and risk assessment of Hedsor Water will be carried out over the next few months.