The Corp didn't operate that system in '71-72. We could have late cars but they were shared and no records kept of who went where sharing with whom. It would have been a bit of a task to divvi up the tax liability between the one that got out at Hanger Lane, the next at Greenford, the next at Litton Avenue, and Meself in South Harrow.
The IR did used to negotiate with individual employers and individual trade unions then. Maybe more so than nowadays when it's "all on the computer".
DG