The Class 701 trains (SWR Arterios), ordered by South Western Railway

 

The Class 701 trains (SWR Arterios), ordered by South Western Railway, took three and a half years from construction to passenger service due to cab design issues, software problems, and Network Rail’s caution. The first Class 701 emerged from the Derby Litchurch Lane factory in June 2020, yet it was to be three and a half years before the first carried passengers.

https://www.railmagazine.com/features-1/swr-s-arterios-are-they-worth-the-wait