While the HST is an icon, a key ingredient the Mark 3 coach would have happened without the HST, so can be considered a massively successful design in itself. Mk3 carriages were the backbone of InterCity, whether as part of an HST or behind a electric loco on the WCML, and still operate on loco hauled services out of Marylebone. Then you have the Mk3 sleepers, the "Inter City" style Class 442 EMU plus the vast number of commuter EMUs and DMUs that are derived from the basic design (317, 318, 319, 320, 321, 325, 455, 456, 150) and still going strong, with the likelihood that hydrogen power will keep some in service for a long time to come