|Weight – Loco||75t 12cwt|
|Driving Wheels||6ft 8.5ins|
|Boiler Pressure||225psi superheated|
|Cylinders||Four – 15in x 26in|
|Valve Gear||Inside Walschaert with rocking shafts (piston valve)|
The first four-cylinder engine on the GWR was No 40 built in 1906 as an Atlantic (4-4-2) engine. It was rebuilt in 1909 as a 4-6-0 engine and renumbered 4000 North Star. It was the first in a long line of GWR four-cylinder express engines which included the Star, Castle and King classes. 4000 was later converted to a Castle class engine.
Seventy-two more engines were built between 1907 and 1914 and in 1922 and 1923. The earlier locomotives were subsequently fitted with new boilers and superheaters, whilst the later engines were built as such. The locomotives were named after Stars, Knights, Monarchs, Queens, Princes, Princesses and Abbeys. Some had the names removed during the war as they had names relating to foreign monarchs.
From 1925 to 1929 5 locomotives (4000, 4009, 4016 and 4032) were rebuilt as Castle class engines. In 1937 -1940 4063-4072 were also rebuilt as Castles and renumbered 5083-5092 but retained the original names.
Three different varieties of steam pipes could be seen fitted to the engines in BR days. Some retained the original inside steam pipes. Others received elbow type steam pipes when the inside cylinders were replaced but the outside cylinders were not. Others had the Castle type of outside steam pipes fitted when they had all four cylinders replaced.
Withdrawal of the class commenced in 1932 and all apart from the one preserved were withdrawn by the end of 1956.
Accidents and Incidents
On 15 April 1923, locomotive 4048 Princess Victoria was hauling a freight train that was in a head-on collision with a passenger train at Curry Rivel, Somerset due to a signalman’s error. Nine people were injured.