How could you possibly know that? Even if they do immediately take the innocent person's word for it, which they quite possibly won't especially if the offence is towards the more serious end of the scale, they certainly wouldn't tell them they are just dropping it and not going after the real offender.
That is exactly what happens. It is up to the train company to prove who was stopped and they will have no evidence to the contrary if they didn’t ID the person at the time. We see this all the time on the forum.
Very often, because the company has not identified who was stopped, the matter simply has to be closed because there is no evidence.
The OP has been very naughty indeed. People in this part of the forum do sometimes like to moralise which can lead them to invent ideas like the police coming after you for theft (won’t happen here) or, somehow, they will monitor CCTV (constantly?) to see if your grainy features match up with some random person they stopped, likely many weeks after it happened (!). But those things don’t happen and we don’t live in that world; advising the OP to immediately dob themselves in might make one feel better but it isn’t in the OP’s interests to do this when the outcome is inevitably to be prosecuted and fined.
So the question here is “what is in the OP’s interests?” Given what we know, it is to simply leave the matter alone and not contact TfL begging to be prosecuted, although I do think they might like to let the old flatmate know they gave their details. But they don’t *have* to do this either.
What does occur to me is that TfL are known to actively check CCTV and wait at the barrier line for suspected offenders. What I don’t know is whether they use a similar approach when it turns out that they have been given incorrect details. But because I don't know, I can't discount the possibility.
TfL do this with people who are habitual offenders who travel on a set commute and arrive at the station at say, 8am. They already know who these people are because they are committing offences and already have intelligence on them. That’s the important part.
None of this applies to the OP; the only thing they have is a low quality video, and they might not even have that after several weeks. The OP might want to lie low and not use that station for a bit, but the chances of this coming back to bite them are virtually nil. As I often say, we don’t live in the panopticon.
