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Also known as Low Matlock Rolling Mill, Loxley, Sheffield
The Wikipedia entry gives a good and thorough account of the mill and its history 
The mill was used for water-powered rolling until 1956, latterly under the ownership of Kenyon Brothers. The overshot waterwheel was 18 ft 6" diameter and 11 ft 8" wide. This drove the mill stands through an impressive train of gears and a flywheel. The gearing was supplied by the 'Salford Works of David Brown' (i.e. P. R. Jackson and Co). The mill was bought by Barworth Flockton in 1974, and sold on to Firth Rixson in 1997. Operations ceased in 1999. 
The rolling mill is now owned by Pro-Roll Ltd, who use it for hand rolling high grade bar. The roll stands are now motor-powered. The Pro-Roll website includes a good video of the rolling process