For many years, right up to 1959, a Midland design of 4-4-0 class 2P was the mainstay of the express passenger traffic, with variations of 3F 0-6-0 freight tender engine and 0-6-0T tank engines. A revolutionary change took place when the Midland built a small fleet of 2-8-0 tender engines to handle the heaviest freight trains—the unique S&DJR 7F 2-8-0 series—with Walschaerts valve gear and the greatest tractive effort ever delivered by a Derby locomotive, with the exception of the "Lickey Banker" 0-10-0.