Thank you for answering.
This sequence of actions is common amongst fare evaders and is often referred to as “doughnutting“, where tickets are held (or PAYG used) to cover the start and end of a journey but a hole is left in the middle. Revenue Protection Inspectors regularly keep watch at the ticket gates at Stratford International, where the pattern of train calls (three eastbound followed by three westbound most of the day) makes it quite easy to spot and intercept people who touch out on the barriers coming off a westbound train, and check whether they are using an ITSO card (which would usually be allowed) or an Oyster or contactless card (which would not).
I am not however of the view that you have in fact committed any offence here, as based on what you said, you:
- Held a valid ticket when you joined the train
- Showed your ticket when you were asked to do so
- Did not have an intent to avoid payment of the fare, as you thought (albeit incorrectly) that your actions would lead to you paying the correct fare
However the fare of £18.30 from Ebbsfleet to Stratford International remains outstanding and should be paid as soon as possible, and needless to say, you must be certain to buy the correct ticket in future as you will no longer be able to have the excuse that you “didn’t know”.
You will also need to be careful when responding to correspondence from Southeastern that you do not inadvertently incriminate yourself; we would suggest posting your reply here in draft prior to submitting it (remove all personal information of course) so that we can advise on it.