Several sub-classes of Class 31 exist: These first 20 locomotives, originally numbered D5500–D5519,[8] were always easily recognisable as they did not have the headcode box mounted on the roof above the cab, leading to the nickname "Skinheads".

[citation needed] These pilot scheme locomotives were non-standard in having Electro-Magnetic Multiple-Working control equipment, and were limited to 80 mph (130 km/h).

After being involved in a serious collision D5518 was rebuilt in September 1967 as a standard locomotive, with indicator boxes, and blue star coupling code.

The whole sub-class had steam heating boilers fitted, had the Blue Star Electro-Pneumatic multiple-working controls as found on many other BR classes.

The Class 31/1s could be found on a variety of secondary and relief passenger duties as well as parcels and freight traffic.

Locos were also allocated to Bristol Bath Road and Old Oak Common on the Western Region, where they could be found working passenger trains as far west as Barnstaple and Paignton.

[15] In the early 1980s Healey Mills and Bescot on the Midland Region also gained an allocation as replacements for Class 25s.

They had an ETH index of 66, equivalent to 330 kW, which was sufficient to power trains of up to eleven Mk 3 carriages.

This allowed them to pre-heat long trains moving between depot and a station for a service to be worked by a larger locomotive.

When ETH was being supplied, the traction power output of the 31/4 subclass was therefore limited to around two-thirds of that of the non-ETH variants; this did not help the performance of an already somewhat underpowered locomotive.

Only 31530 (Sister Dora), 31544 (Keighley and Worth Valley Railway) and 31568 (The Engineman’s Fund) were named when numbered as a 31/5.

Class 31s were first used on the Western Region in 1969 when D5535 was allocated to Old Oak Common to work Empty Coaching Stock (ECS) trains into Paddington.

31255 became the locomotive for the EWS livery paint trials but never ran on the main line and spent its life at Toton until being preserved in January 1999.

In 1999, Fragonset won a short-term contract with Silverlink for two locomotives to work in top and tail mode with two Mk.

Regular work at this time included use hauling Class 317 electric multiple units from West Anglia Great Northern's Hornsey depot to Bedford for use with Thameslink.

With the overhaul and entry into service of Network Rail's own locomotives, these two engines were returned to Fragonset.

Locomotive 31106, formerly Spalding Town, is privately owned by Howard Johnston, and after a period of lease to Fragonset, FM Rail, and RVEL which included extensive main line running for 11 years, including working as far north as Oban in Scotland, is based at the Weardale Railway.

Johnston purchased three more of the class from EWS, but they acquired new owners; 31107 (scrapped by C F Booth at Rotherham in May 2009, following a staged collision with a Renault Espace on a level crossing during Top Gear Series 9, Episode 5 in 2006 to demonstrate the danger of trying to beat a train at a crossing), 31289 (preserved at the Northampton and Lamport Railway), and 31301 (scrapped).

In August 2018, Network Rail offered its final two Class 31s (31105 and 31233) for sale; both were purchased for preservation at Mangapps Railway Museum in Essex.

The rear locomotive slowed down to a stop and 31107 continued to coast at a speed of 70–80 miles per hour into the road vehicle parked across the eastbound 'up' line.

For the crash, locomotive 31107 received a special black livery with the slogan "Level crossings — Don't run the risk" along the side in white lettering.

The final 5 minute segment was originally scheduled for 4 February 2007 but was rescheduled, apparently due to a fatal crossing crash at Dingwall two days earlier.