SECR B Class

The SECR B Class was a series of inside-cylinder 4-4-0 express passenger locomotives designed by James Stirling for the South Eastern Railway and introduced from 1898, representing the SER's principal express type in the final years before the merger of the South Eastern and London, Chatham and Dover Railways to form the South Eastern and Chatham Railway in 1899. The B Class was Stirling's attempt to provide the SER with a capable inside-cylinder 4-4-0 for the railway's Kent coast expresses and Continental boat trains — the services to Dover and Folkestone that connected London with the Channel ferries to France and Belgium and were among the most commercially prestigious on the South Eastern network.

Stirling designed the B Class with inside cylinders and his characteristic domeless boiler — the family feature shared with his brother Patrick's GNR designs and his own SER O Class goods locomotive — giving the B Class a clean and distinctive appearance. The 6 ft 6 in coupled wheels gave adequate speed for the boat train timings, while the inside-cylinder layout maintained consistency with SER workshop practice at Ashford. The B Class worked the principal SER express services from 1898 until the working union with the LCDR from 1899 gave the combined SECR management access to Wainwright's improved designs.

Under Harry Wainwright, who became SECR Locomotive Superintendent after the working union, the B Class was progressively supplemented and then replaced by the more capable D Class and E Class 4-4-0 express types from 1901. None of the B Class was preserved, though the SECR express tradition is represented by Wainwright's D Class and E Class examples at the Bluebell Railway and other heritage railways.