The biggest (but not the longest, that was at Ross, Bacup) rope drive in Lancashire was the Mons Mill engine at Todmorden. Here's the entry from Arthur Roberts' Black Book and my additions for 'Steam Engine Research Resources', published on Lulu.com..
[Originally called Hare Mill but name changed to Mons when Carel invested in firm.] Sam Mathews[sic], Lancashire Cotton Corporation. Mr H Haigh. 3000hp cross compound engine by Carel Freres of Ghent, Belgium, 1913. 39 ¾”HP. 72 5/8” LP. X 4ft 9 ½” stroke. 160psi, 80rpm. Drop valves on both cylinders. 25ft flywheel, 70 ropes. Trunk guides and tail rod supports. Cylinder steam-jacketed. Airpump LP side from HP crankpin. Water-cooled main bearings. Mishap to barring engine (1961) new one bought from Moston Mill. [George Watkins reported but 4ft 7 ½” stroke. Designed to run the double mill at 200psi but second half never built because of subsidence and bad trade. Five boilers installed with room for two more for full installation. Flywheel 13ft 8” wide for 69 ropes. Weighed 130 tons with crankshaft. Engine dismantled in 1964 and mill closed in 1968. Newton Pickles saw engine running and said it was rough and a wastrel, no doubt partly because it was running below designed pressure and load. This was the largest Carel engine brought into Lancashire.]