37215

37215 (D6915) is a Class 37/0 owned by The Growler Group, built at the English Electric Vulcan Foundry in Newton-le-Willows in 1963.

On entering service, D6915 was allocated to work predominantly freight trains around the Swansea and West Wales areas. This lasted around three and a half years, though the locomotive lost its steam generator in early 1965 — barely twelve months after construction — when the Western Region's Chief Mechanical & Electrical Engineer released generators from a number of in-service South Wales locomotives, following an earlier decision to recover those intended for new-build D6948 and its siblings.

In October 1967, the locomotive transferred north to Wakefield shed in West Yorkshire, moving two months later to the newly built Healey Mills diesel depot. From there it worked coal and other freight services around Yorkshire and across the Pennines into Lancashire. It lost its 'D' prefix in October 1968, and four years later, in October 1971, moved to Tinsley depot near Sheffield.

A transfer to Stratford in East London followed in September 1973, beginning just over eight years working the Great Eastern lines out of London and into East Anglia. This included servicing the many freight facilities across Essex and the north Thames-side area, with regular forays around the North London Line onto Southern and Western Region territory. The locomotive was renumbered from 6915 to 37215 in March 1974.

In January 1982, 37215 returned to Yorkshire and Tinsley depot. For nearly six years it was a frequent sight in the area, becoming a summer Saturday regular on the extra holiday trains that ran from the Sheffield area to Blackpool, Scarborough and Skegness.

The sectorisation of BR's locomotive fleet brought three rapid moves between November 1987 and May 1988 — from Tinsley to Immingham, then Stratford, and finally Cardiff Canton — as 37215 became part of the Trainload Petroleum fleet. It spent the next four years hauling heavy oil trains out of South Wales to terminals across the south of England, usually paired with other Class 37s.

The locomotive was finally stored in August 1992 and moved to Inverness depot, where it was officially withdrawn on 16th July 1993. It was purchased by The Growler Group and arrived at Toddington in June 1994, restored to full working order by 1998. In 2007 it received a high-quality repaint into BR Blue livery as carried by the class during the 1970s and 1980s, and 2023 marked the significant milestone of 25 years in active preservation service.