The British Rail built class 26 was ordered along with a number of other pilot scheme Diesels in the 1950s with delivery taking place between 1958-1959.
47 Locos were ordered and Birmingham Railway Carriage and Wagon Company in Smethwick (BRCW), were awarded the contract.
BRCW had primarily constructed Diesel Multiple Units for rural passenger services previously and in this instance this was a unique operation in loco building as BRCW went into a partnership arrangement with Swiss Company Sulzer Brothers of Winterthur, they had constructed a dozen locos for CIE in Southern Ireland previously in 1956-57.
The Sulzer 12LDA with four Crompton Parkinson Traction Motors was deemed a suitable power unit for these successful engines, an equivalent power unit was used in Class 24 locos, this was rated at 1160hp.
Initially a batch of 20 locomotives then numbered D5300-5319 were constructed and these were to be evaluated at Hornsey Depot in North East London initially on suburban commuter trains and Empty Coaching Stock duties.
They were all delivered in British Rail Green with grey roofs and a thin white bodyside stripe.
Locos were moved to Finsbury Park (North London) a purpose built Diesel shed in 1960, although one class member D5303 was borrowed by the Scottish Region and based at Inverness, Eastfield (Glasgow) and Leith sheds for a period in 1958.
A further 27 production locos numbered D5320-D5346 were delivered to Scotland between April and October 1959, these were mainly shedded at Haymarket (Edinburgh).
After evaluations were completed in the period up to Mid 1960, it was decided to shed the whole class in Scotland and D5300-D5319 were allocated to Haymarket and the Haymarket allocated locos moved to Inverness.
The locos were best described as mixed traffic and could be found on Parcels, Short lightweight freight workings and passenger workings all over Scotland.
They rarely strayed from Scotland, although examples did appear at Carlisle on a regular basis and even ended up in Newcastle on a few occasions.
When Cockenzie Power station was opened in 1967, an air braked type of loco would be required and D5300-D5306 were chosen to be fitted with slow speed control equipment to work Coal Hopper (MGR) trains into the Power Station, these class were to be associated with this work for most of the rest of active BR service.
The remaining locos were to remain synonymous to Scotland but rarely found themselves on unusal workings, they remained happy plying to Kyle of Lochalsh, Thurso, Wick and Carlisle steam heating short trains of carriages and keeping the passengers nice and warm as well as comfortable in mark One carriages.
The only early casualty was D5328 which suffered an accident in 1972 and was subsequently scrapped.
With the advent of TOPS locos were numbered 26001-019 and 26021-26046 and gradually these locos were painted into BR Blue livery.
As other classes became surplus the class found themselves relegated to other duties and although they were refurbished in the 1980s and repainted in Railfreight livery and in the case of 26001-26007 which received Coal Livery as they still continued to work MGR trains.
Finally as the class were basically being used by the Civil Engineers on ballast Trains and Engineering Trains they were to receive Dutch Livery with Yellow Upper Bodysides these were repainted in 1990-1992.
Finally in 1992 26001/007 were repainted back into Green original Livery and they worked a number of special passenger Trains, including a weekly timetabled diagram to the Kyle of Lochalsh again.
The class was finally eliminated in 1993 and became part of railway History.
13 Class members survived into preservation and can be found in various states of repair around Preservation sites in the whole of the UK, six of the 13 are operational and the familiar Sulzer Beat can still be enjoyed at these Heritage sites at different times of the year.