Advance fares are valid only on the date and train shown on the ticket and are non-refundable. You can change the time or date of travel before departure of the first reserved train.
Any difference in fare and an administration fee will be payable.
As the whole reason for me needing to postpone it was that I was unexpectedly busy, heading to the station before the train wasn't an option. I don't therefore know if it was a website issue, or I'd misunderstood the change option on the ticket.
So, for an Advanced Purchase ticket, under what conditions can you change to a different AP ticket, how, and until when?
If the online system does not permit a change, that may be due to software limitations. Under such circumstances, I would contact the TOC where you bought the ticket by phone or online chat to request to change the ticket.
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