This sounds a simple question. It turns out that the answer is much more complicated.
If you have an Off-Peak Day Return from Sevenoaks to London Terminals then it’s the 0919 from Sevenoaks to Charing Cross.
But if you have an Off-Peak to somewhere else then it may not be valid on the 0919 – or the 0929 either!
An SRTA investigation has established that there are (at least) four different rules that apply, and they depend on the destination on your ticket. The rules are difficult to find on the National Rail Enquiry and Southeastern websites (although the rules are used by those websites in determining whether to offer you an Off-Peak fare once you have given a specific origin, a specific destination and a specific time.)
For Off-Peak Day Returns from Sevenoaks to London Terminals tickets are subject to Restriction Code BC. This specifies that for outward journeys (to London) the ticket is not valid on trains timed to depart Sevenoaks before 0915. So the ticket can be used on the 0919, but not on the 0913.
In fact there’s a special rule here for Sevenoaks: “BC” off-peak day tickets are valid from 0906 from other places, including Tonbridge!.
But for Off-Peak Day Returns to other places the rules are different.
For example, an Off-Peak Day Return from Sevenoaks to Reading is subject to Restriction Code B1. This specifies that for outward journeys the ticket is not valid on trains timed to depart before 0930. So it’s not valid on the 0919, 0922 or the 0929.
Yet for a similar day journey through London, to Cambridge, a different rule applies. An Off-Peak Day Return from Sevenoaks to Cambridge is subject to Restriction Code C4. This specifies that for outward journeys the ticket is not valid on trains timed to arrive at London Terminals before 1000. London Bridge counts as a London Terminal (even though it’s not a Terminal for Southeastern services – that’s another story). So it’s not valid on the 0919 or 0929 to Charing Cross, which are timed to arrive at London Bridge at 0941 or 0953 respectively. But the off-peak day return ticket is valid on the 0922 to Blackfriars (timed to arrive at Blackfriars at 1029).
But there’s a further catch. If you’re staying overnight in Cambridge and coming back the next day, then you would need an “Off-Peak Return” rather than an “Off-Peak Day Return”: the return portion of an Off-Peak Return is valid for a month. Yet for Cambridge the rules for a Off-Peak Return are different. Restriction Code 4A applies. This specifies that the ticket is
not valid on trains timed to depart before 0930 – so you could not use the 0922 to Blackfriars, even though you could do so on a Day Return.
Moreover long-distance Off-Peak return tickets have rules geared to the time of the onward train from London. So, for instance, a Sevenoaks to Truro (Super) Off Peak Return has Restriction Code YX. That specifies that it is not valid on trains timed to depart London Paddington before 1003 (and after 1510 and before 1901). So using this ticket for the 1003 from Paddington National Rail Enquiries validly suggests the 0831 from Sevenoaks. Indeed the ticket could be used on any morning peak-time train.
There’s an additional gotcha to consider. The rules apply to the timetable times of the trains, not the actual times. So if you are waiting on the platform at Sevenoaks for the 0943 to London and a late-running 0929 comes through at 0940 then your ticket to Reading or Cambridge won’t be valid on it.
We don’t consider that information about the validity of tickets is communicated well by the rail industry. The complexity of the system is probably as baffling to front-line staff as to customers.
Moreover if the purpose of off-peak fares is to encourage travel out of the peaks, it’s counter-intuitive that a train, that is valid for an off-peak day return to London, is not valid for an off-peak day return to somewhere else via London, even though the onward journey would be even further from the morning peak period.