Five units have been converted for the Island Line to replace the Class 483 sets, with the first delivered for testing in late 2020 and the second in May 2021.

The line closed in January 2021 for upgrade works and was originally scheduled to reopen on 1 April 2021 with the new fleet of trains,[5] but delayed infrastructure work as a result of the COVID-19 pandemic extended the shutdown period by six weeks to 13 May 2021,[6] and then problems with software on the trains further delayed their introduction.

[9] From 1989 onward, rail services were operated using Class 483 units, which originated as 1938 tube stock and last ran on the Northern line.

This made them increasingly difficult to maintain, with the original fleet of eight eventually reduced to four in service, with another two retained as spares donors.

This requirement was eventually linked with a wider need to invest in improvements in the line itself, and saw suggestions that it might be converted to a light rail operation, or even a bus rapid transit route.