SECR 118 Class

The SER 118 Class was a series of inside-cylinder 2-4-0 passenger tender locomotives designed by James Cudworth, Locomotive Superintendent of the South Eastern Railway from 1845 to 1876, and built from 1864 for the SER's secondary passenger and semi-fast services across Kent and Surrey. Cudworth was a distinctive figure in Victorian locomotive engineering for his advocacy of the firebox coal-burning equipment that bore his name — the Cudworth firebox — which represented one of the earlier serious attempts to burn coal rather than coke in locomotive fireboxes, addressing the cost and supply advantages of coal over the coke that early Victorian locomotives had required to avoid the black smoke that coke-burning suppressed.

The 118 Class used Cudworth's characteristic inside-cylinder layout with the coupled wheels positioned relatively far forward, giving a mechanical arrangement that differed from the contemporary Stephenson standard in subtle but distinctive ways. The locomotives were suited to the SER's varied secondary passenger duties across the Kent network: the stopping services between London Bridge and the Kentish coastal towns, the semi-fast services to Canterbury and Dover, and the branch lines that served the rural Kent hinterland that the SER had developed through the 1840s–60s.

Cudworth retired in 1876 and was succeeded by James Stirling, whose more modern designs progressively displaced the Cudworth classes from all but the most minor duties. The 118 Class gave the SER's secondary passenger services through the 1870s until replacement. None was preserved, though Cudworth's engineering significance — particularly his coal-burning firebox work — is well documented in railway engineering history.