British Rail Class 27

The BR Class 27 was a family of sixty-nine Bo-Bo diesel-electric locomotives built in 1961–62 by the Birmingham Railway Carriage & Wagon Company (BRCW) of Smethwick, powered by a Sulzer 6LDA28 six-cylinder engine producing 1,250 hp. The class is most strongly associated with Scotland, where the majority of its allocation was concentrated from an early stage and where it remained until the end of its BR career.

The BRCW body design was a distinctive alternative to the BR Derby standard, with a characteristic cab front treatment and a windscreen arrangement that gave the Class 27 a characterful appearance. The locomotives were fitted with electric train heating equipment from new — an important distinction from the steam-heated Class 25 — making them suitable for passenger services on routes where electric-heated coaching stock was used.

The Scottish allocation of Class 27s was concentrated at Eastfield depot in Glasgow, from where they worked the Edinburgh–Glasgow push-pull passenger services using converted locomotive-hauled coaches, Highland main-line freight, and general mixed-traffic work. The push-pull operation was particularly notable — Class 27s fitted with push-pull equipment worked ScotRail's Edinburgh–Glasgow Queen Street services from 1971, providing frequent inter-city operation that raised standards considerably before electrification.

Withdrawal began in 1985 as the Class 37 and newer diesel types displaced the 27s from their remaining Scottish duties, and the last examples were retired in 1987. Six examples survive in preservation, with several having been restored to working order on heritage railways. The Caledonian Railway at Brechin holds the largest concentration.