Based on the Hitachi A-train design, 13 five-car units were built to replace Class 221s on services between London Euston, Birmingham New Street and stations on the North Wales Coast lines.

[11] The trains will be maintained by a joint team of Alstom and Hitachi staff, alongside the Class 807, at Oxley depot near Wolverhampton.

[13][14] Main line testing of the Class 805 commenced in February 2023,[15] while the type's introduction into service originally planned for later that same year.

[1] In August 2024, the Office of Road and Rail (ORR) issued an improvement notice to Avanti West Coast regarding the operation of the newly-introduced Class 805 fleet, having determined its lack of an automatic speed supervision system (which was present on the preceding Class 221 fleet) to be in breach of legislation.

Compliance with the improvement notice would require all Class 805s to be retrofitted with some manner of continuous speed supervision; if this functionality necessitates the installation of additional hardware, such work could be quite costly to implement.