The original fleet of these 4-car outer-suburban sets were built for the St Pancras-Bedford (Bed-Pan) electrification project and were based closely of the Mk3 coach design of the period. The 48 sets were allocated to Cricklewood and did not enter service without problem. Major industrial action over their use under driver only operation saw a huge delay to introduction. After the sets did go into traffic serious technical problems befell the fleet with the transformers falling off the pantograph vehicles, this required a major refit at BREL Wolverton Works.
By 1985 a further fleet of 18 Class 317 sets were authorised for use on the Great Northern routes out of Kings Cross, these incorporated some revised body structure and a new front end design, these sets were classified as 317/2.
Changes in rolling stock deployment and the introduction of Thameslink services covering the London-Bedford suburban routes saw the Class 317/1s transferred to Hornsey for Great Northern operations.
Following privatisation of the railways the deployment of the fleet has again changed, this saw the 317/1 fleet retained in near original form but refurbished for Great Northern (now WAGN) operation while the 317/2 fleet were fully refurbished and upgraded and reclassified as 317/6s, these are also deployed on WAGN services.
Following the introduction of a revised Liverpool Street-Stansted Airport Airport service in 2000 a batch of nine Class 317/1s were fully refurbished by Railcare Wolverton and now incorporate a a revised front end, catering stacks and luggage racks.
Originally the Class 317s were delivered in standard blue/grey livery, this later gave way to NSE colours and recently two different versions of WAGN livery have been applied as well as a dedicated Stansted Airport livery.