The Iron Duke; which is what gave the class or type of locomotive its official name.

The Great Western Railway Iron Duke Class 4-2-2 was a class of broad gauge steam locomotives for express passenger train work built during the 1840s in the UK.

It was one of the very first types of major, mass-produced steam locomotives produced in the UK.


The prototype locomotive, Great Western, was built as a 2-2-2 locomotive in April 1846, but was soon converted to a 4-2-2 arrangement, with the leading wheels set rigidly within the sandwich framing, rather than in a separate bogie. The remainder of the class entered service between April 1847 and July 1855.

Locomotives of the Iron Duke class were extremely fast and had an estimated top speed of about 80 mph (133 km/h). They were used to haul the Flying Dutchman express train which, for several decades, was the world's fastest train. In 1852 the daily service from London Paddington Station to Exeter (194 miles) was achieved with an average speed of 53 mph (88 km/h), and the flatter section between London and Swindon covered at an average speed of 59 mph.

In May to July 1870, three locomotives (Great Britain, Prometheus and Estaffete) were extensively rebuilt with new frames and boilers, but retaining their original names. Following these, further locomotives were built to similar specifications, entering service between August 1871 and July 1888. These new locomotives are generally referred to as the Rover class. Although these locomotives took the names of withdrawn locomotives of the original design, they were not rebuilt from them like the first three, but entirely new locomotives (though it is believed that Rover, Swallow and Balaklava may have included some parts from the earlier locomotives of those names).


1985 replica of Iron Duke locomotive. Taken at the Maritime Heritage Centre alongside the Great Western Dockyard, Bristol for the duration of the Brunel 200 celebrations.

Apart from the three conversions, the original locomotives were withdrawn between December 1870 and June 1884. Lord of the Isles (the last to be withdrawn) was initially preserved by the GWR at Swindon Works, but was scrapped in January 1906 owing to pressure of space. The three conversions were withdrawn between September 1880 and October 1887, while the other locomotives to the later design were all withdrawn with the end of the GWR broad gauge in May 1892 (except Hirondelle, which had been withdrawn in December 1890).

Many of the nameplates can be seen at the National Railway Museum and at Swindon Steam Railway Museum, while the driving wheels from Lord of the Isles can also be seen at Swindon.


2-2-2 Great Western

The prototype for this class was named the Great Western and built in 1846. Named after the railway, it was designed to show how the 2-2-2 express engines could be improved; its 8-foot-diameter (2.4 m) driving wheels were a foot larger than those of the successful Fire Fly class. It broke its leading axle after a short while in service and was subsequently rebuilt as a 4-2-2, becoming part of the Iron Duke class.



Iron Duke replica view, at Bristol.

In 1985 a working replica of Iron Duke was constructed using parts from two Hunslet Austerity tanks as part of the Great Western 150 celebrations. The boiler certificate has expired so it cannot currently be steamed.


  • From about 1865, the Iron Duke Class was known as the Alma Class.
  • The replica is normally housed at the National Railway Museum at York, although it has also visited the Didcot Railway Centre,and is steamed up on special occasions, which has a section of broad gauge track. In 2006 it has been moved to Bristol where it is the centerpiece of the Nine Lives of Isambard Kingdom Brunel exhibition in the Maritime Heritage Centre adjacent to the SS Great Britain.
  • In January 2010, the replica arrived at the Gloucestershire Warwickshire Railway where it will form part of a static display of Great Western Railway locomotives celebrating the 175th anniversary of the GWR.