Worsdell class D20
The North Eastern Railway class R (LNER class D20) was a 4-4-0 steam locomotive designed by Wilson Worsdell for express passenger services and introduced in 1909.
The class D20 was designed by Wilson Worsdell for the North Eastern Railway (NER) in response to increasing passenger train sizes on the East Coast Main Line at the end of the 19th century. It was an enlarged 4-4-0 design, building on features from earlier locomotives like the class D17, but incorporating new developments for improved performance. The locomotives had 19-inch diameter cylinders with a 26-inch stroke, Stephenson valve gear, and newly developed outside admission piston valves fitted below the cylinders. The boiler pressure was increased to 200 psi, with a 4 ft 9 in diameter boiler and a 7 ft long firebox, making it the largest NER boiler at the time.
A total of 60 locomotives were built at Gateshead Works in six batches between 1899 and 1907. The initial batch of ten was followed by two batches of ten each in 1900–1901, and three batches of ten each in 1906–1907. The final locomotive, No. 1235, was fitted with an experimental Sisterton superheater, which was later removed after trials proved it unsuccessful.
Superheating was introduced to the class D20s starting in 1912, initially using Schmidt superheaters, with some later fitted with Robinson superheaters. By 1923, only two locomotives remained un-superheated, which were eventually upgraded in 1925 and 1929. In 1936, some locomotives were rebuilt by Gresley with long-travel piston valves and classified as class D20/2, while the un-rebuilt locomotives were classified class D20/1.
The class D20s were highly successful on express passenger services, demonstrating exceptional reliability and versatility. They were dual-fitted with Westinghouse air brakes and a vacuum ejector for alternative train braking.
After the 1923 Grouping, the class passed to the London and North Eastern Railway (LNER) and later to British Railways in 1948, with 46 class D20/1 and three class D20/2 locomotives entering BR stock. Withdrawals began during World War II, and the last class D20 was retired in 1957, with none preserved.
