Once up and running in 2012, the Archimedes screws, the largest in the UK and designed to be fish-friendly, will generate 300kW of energy every hour for up to half of the royal residence. Any surplus electricity will be sold back to the national grid by the developer Southeast Power Engineering Ltd (SEPEL) for use in homes in Windsor.

The largest hydropower scheme in the south east of England is being built by Jackson Civil Engineering for SEPEL and is set to cut annual carbon dioxide emissions by 790,000kilos.

To help ensure the £1.7million project both generates clean energy and improves the local environment, the Environment Agency – who permits and will regulate the scheme – is requiring a new fish pass to be installed at the Weir. The new pass will enable over 12 species of fish including trout and perch, as well as endangered eels, to migrate up this stretch of river – some for the first time in over 200 years.