They are a variant of British Rail's standard 1972 design for suburban EMUs derived from PEP stock, which eventually encompassed 755 vehicles over five classes (313, 314, 315, 507 and 508).

With the Class 502 units life-expired, unable to cope with the demands of the new Link tunnel and approaching 40 years old, by 1977 a replacement was sought.

Owing to the success of the Class 313 fleet on suburban services from King's Cross, four sets were temporarily transferred to Merseyside and based at Hall Road TMD.

The first set was delivered to Birkenhead North depot during September 1978,[9] with the first test run taking place on 9 October 1978.

[11] Unit 507033 was the last Merseyside set to be refurbished, entering service having been named Cllr George Howard in August 2005.

After the introduction of high back seats during refurbishment in 2004/2005 this was reduced to 192 with space for cyclists and disabled people improved.

[17] The fleet received a refresh package including external re-livery, internal enhancements and engineering work.

[18] In January 2016, Merseytravel announced the short list of companies bidding to build new trains which will replace the Class 507 and 508 on the Merseyrail network.

[22] A crowdfunding campaign to raise £10,000 to move the train by road to the Nant Mawr visitor centre at the Tanat Valley Light Railway was set up by the society in May 2024.