SECR F Class

The SER/SECR F Class was a series of inside-cylinder 4-4-0 express passenger locomotives designed by James Stirling and built at Ashford Works from 1883, representing the South Eastern Railway's first systematic 4-4-0 express type and the locomotive class that worked the SER's principal Kent coast and Continental boat train expresses through the late Victorian era. The F Class was Stirling's definitive express design for the SER, applying his characteristic domeless boiler and clean inside-cylinder 4-4-0 proportions to the demands of the Dover and Folkestone boat trains and the Folkestone, Ramsgate, and Margate coastal expresses that were increasingly important to the SER's commercial prosperity.

Stirling designed the F Class at Ashford in 1882–83, specifying the 4-4-0 wheel arrangement that was by the early 1880s becoming the British express standard, with a leading bogie for stability at the moderate-to-high express speeds of the SER's main lines. The domeless boiler — a Stirling family feature shared with brother Patrick's GNR designs, though applied entirely independently at Ashford — gave the F Class a distinctive profile different from the domed boilers of most contemporary express types. The 6 ft 6 in coupled wheels gave adequate speed for the boat train timings.

In service the F Class gave the SER significantly better express performance than the earlier Cudworth 2-4-0 types it succeeded, and the class worked the principal SER express duties through the late 1880s and 1890s. After the SECR working union in 1899, Wainwright's D and E Class 4-4-0s progressively took over the principal express workings, but the F Class continued on secondary express and semi-fast duties. One example, No. 31163, is preserved at the Bluebell Railway.