© Licensed to London News Pictures. 20/12/2011, Windsor, UK. The screw is lifted from a floating barge. One of the two giant 40 tonne Archimedes screws is lifted into place at Romney Weir on the River Thames. The screws, the largest in the UK and fish friendly, will generate 300 kilowatts of energy every hour to power Windsor Castle. It is the largest hydropower scheme in the South East of England. Photo credit: Stephen Simpson/LNP