At the moment, Harrow (-on-the-Hill / & Wealdstone) is served by Class 710s, which came into service in 2019, 730s (2023), S8 Stock (2010), with 805s and 807s (last year) passing through... and 165s (1991), 168s (1998) and 1972 Stock. That gives an age gap of 52 years between 1972 Stock and 805s and 807s. Excluding heritage railways and railtours, which other examples are there of large age gaps between rolling stock running alongside (I know it isn't technically on the same line in this case) each other?
- When S8 Stock trains started running, the A Stock had been there since 1961, for a difference of 49 years
- 803s entered service in 2021, 41 years after Tyne & Wear Metro Metrocars / 599s
- Any rolling stock serving Partick introduced between 1948 and 1977 would beat the examples I've thought of, counting the Glasgow Subway