Under the 1955 BR Modernisation Plan or 'pilot scheme' there was no provision made for a locomotive in the 1500hp-1800hp power range and once the 'pilot scheme' locomotives entered traffic, it quickly emerged that there was a requirement for a more powerful Type 3 locomotive. As a result of this, in 1959 an initial order for 42 mixed traffic locomotives was placed with English Electric and subsequent 'follow-on' orders over the next 5 years resulted in 309 examples of what was to become the Class 37 being built.
Built in 1962 at the Vulcan Foundry and entering service as D6737 the loco’s first depot allocation was Hull Dairycoates, a number of re-allocations followed over the years remaining an Eastern Region locomotive until 1981. Transferrred to Scotland the locomotive became part of Glasgow Eastfields allocation for use on the West Highland line and the locomotive retained an operational boiler until transfer to Motherwell in 1985. Allocated for dedicated use on the Ravenscraig steel traffic, the locomotive was renumbered, named and had both boiler and vacuum exhausters isolated and could often be found triple heading the heavy iron ore trains between Hunterston and Ravenscraig. Renumbered back to 37037 following the disbanding of the dedicated pool in 1988, the locomotive was based predominantly on the Western Region until transfered to Toton and stored as surplus in 1999.
Allocated to the WKMF pool – EWS Headquarters Class 37 Special Projects in July 1999, the locomotive was transferred to France in August for a 12-month lease for use in the construction of the TGV-Mediterranee rail link. Returning to the UK a year later, the locomotive was transferred to Wigan CRDC and remained there until allocated for disposal in March 2003.
The locomotive was purchased by HNRC in August that year and sold to the DDS on 1 January 2004 and as part of the purchase, HNRC staff at Barrow Hill returned the locomotive to an operational condition. Following successfully testing at Barrow Hill, 37037 moved south and arrived at the SDR just before the 2004 diesel gala where it gave a faultless performance and its “tatty grey” livery proved popular with visiting enthusiasts.
Under the ownership of the DDS, the locomotive has visited a number of preserved railways across the UK and has been backdated to D6737 in as near to original condition as possible. Following a lengthy running period in BR Green the locomotive has been stopped for maintenance. In addition to the partial re-wire of the locomotive and overhaul of No 2 end electrical machines, areas of the body have been repaired and the locomotive repainted as 6737 but now wearing BR blue livery.