Highland Railway Castle Class

The Highland Railway Castle Class was a series of 4-6-0 express passenger locomotives designed by Peter Drummond, Locomotive Superintendent of the Highland Railway from 1896 to 1911, and introduced at Lochgorm Works, Inverness, from 1900. The Castle Class was the Highland Railway's principal express passenger type of the Edwardian era, named after the ancient castles of the Scottish Highlands and bringing 4-6-0 express power to the demanding single-line routes through the northern mountains.

Peter Drummond was the brother of Dugald Drummond, who had himself transformed Caledonian Railway locomotive practice in the 1880s before moving to the LSWR, and Peter brought similar engineering ambitions to the smaller Highland Railway. The Castle Class represented an ambitious step up in power for the HR: the 4-6-0 wheel arrangement gave six coupled driving wheels for maximum adhesion on the severe Highland grades, while the large boiler produced the sustained steam for the long distances between water stops on the far-northern routes.

The Castle Class worked the Highland Railway's principal passenger services between Inverness and Perth, and the through coaches to Aberdeen and the south, from 1900 until superseded by the subsequent developments of the Drummond and later Smith 4-6-0 designs. After the 1923 Grouping the class passed to the LMS. None was preserved, but the Highland Railway Castle Class represents a significant milestone as one of the earliest 4-6-0 express passenger designs in Scotland.