The Ceylon Government Railway B1-B6 were a range of similar steam locomotive classes used by British Ceylon's (later Sri Lanka's) national rail operator. Formerly designated as the NOA Class before the reclassification of 1937, they were 4-6-0 tender-tank locomotives meant to operate on the Main Line. As of today, only select members of the B1 and B2 classes survive into preservation.^[1][2]

The Class B1 was the last and most modern of these six locomotive classes to be constructed.^[3][4] A total of forty-nine were built for the Ceylon Government Railway from 1927 to 1948. This class had five subclasses apart from the standard model, namely A, B, C, D and E. These locomotives are also known as the Governor Class, owing to the fact that most class members were named after Governors of British Ceylon. In 1936, class member No. 242 Sir Edward Paget was streamlined, but the streamlining was later removed in 1937.^[1] In the 1950s, some members of the class were converted to burn oil instead of coal.

Only two members of the class, No. 251 Sir Thomas Maitland and No. 352 Sir Frederick North, have survived into preservation.^[5] Both are currently operational and are used to haul the Viceroy Special, a chartered excursion train operated by J. F. Tours.

A total of thirty-five members of this class were produced for the Ceylon Government Railway. The Class B2 also had various subclasses excluding the original from A to E.^[1]

Only one member, No. 213, survives into preservation. It is also maintained in working order so as to haul the Viceroy Special.^[5]

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