No.58100 had four cylinders to produce the required power and was by far the largest engine built by the Midland Railway with a tractive effort of 43,000lbs. The outside cylinders were inclined at an angle of 1 in 7 to ensure that all the connecting rods drove on the centre axle. The vertical stanchions at the corners of the front footplate were provided to assist drivers to judge the distance when buffering up to passenger trains, with an electric headlight for use in the dark. Some drivers allegedly switched the light off since it would alert the crew on the train they were to assist that it was ‘Big Bertha’ buffering up, and so they may not work their engine as hard as if it was banked by the tank engines. The new cylinders fitted in 1954 to No.58100 after the originals were damaged when water got into the left-hand inside cylinder are evident in this photograph. The spare set had been cast when the engine was built but had lain forgotten in a dusty corner of Derby Works for forty years. So ‘Big Bertha’ was reprieved, but this was short-lived and it was withdrawn in May 1956 when the crank axle journals were found to be worn beyond scrapping limits and this time Derby had no spares.