The original publicity material for the English Electric Type 3 described it as a 1,750hp diesel-electric locomotive built at Vulcan Foundry. Targeted at mixed traffic work a boiler and a top speed of 90mph permitted their use on express passenger workings as well as freight.

By the end of the 1970s the majority of loco hauled passenger trains were being operated by Electric Train Heating (ETH) stock resulting in many Class 37s, none of which were fitted with ETH at the time, being transferred to a predominately freight role on the railway network.

By the mid-1980s the class, which still played an essential role in BR freight services, had been in operation for more than 20 years. In light of this, discussion of replacement arose but due to the success and reliability of the 37 a programme of refurbishment was chosen instead. Whilst it was envisaged that this refurbishment would cover the entire fleet after only 135 examples had been updated the programme was abandoned.

By 1985 British Rail was being re-organised into sectors which affected the freight as well as passenger businesses. A new livery of Triple Grey was rolled out for freight locomotives and much of the Class 37 fleet was split between the various freight sectors each of which encompassed a particular market.

With the fleet being of such a substantial original size and as a result having such a large operational range, it is no surprise that many Class 37 locomotives have found their way into preservation as the new era of 21st Century Diesel locomotives take over the ever demanding freight railway business.

More than 40 Class 37s can be found in the preservation scene as of 2009, covering a full spectrum of sub classes that evolved of the life of this magnificent locomotive. EWS (now DB Schenker) presented the original locomotive to the National Railway Museum in York to ensure safe keeping for many years to come.