Hydroelectric power is to once again power a Victorian National Trust mansion, just as it did almost 140 years ago. Cragside in Northumberland was the first house in the world to be lit by hydroelectricity when then owner Lord Armstrong used water from the lakes to power arc lamps in 1878. Two years later, the turbine provided electricity to illuminate the library using Joseph Swan’s incandescent light bulbs, achieving another world first. But the system fell into disuse over the first half of the 20th century and in 1945 Cragside moved to mains electricity. Now a modern 17m-long Archimedes screw has been installed that is set to return Cragside to its former glories by providing enough power to light all its 350 LED light bulbs – equivalent to about 10 per cent of the house’s 372,000kWh annual electricity needs.