Interesting, I only ever used paper tickets for this reason, I knew Oysters would be trackable.
Because my daily routine changed when I told them my evading began (start of the year when I started at the gym ((admittedly this only occurred to me this afternoon)) will this make it harder to detect me?
This is the thing, I've worked in central London for 6 years, I've only evaded for 2 of them. If they look at my employment history could they say that I've worked there for 6 years and therefore I owe them 6 years. My previous journeys were also always on paper tickets so once again it becomes hard to prove. I guess it could end up working in my favour that I was honest, or against me in the fact I can't prove I travelled legitimately prior to being caught.
On the first part I have underlined, bear in mind that they may ask you about this. "Why did you use paper tickets rather than Oyster for such regular journeys?" "So it couldn't be tracked" is not a good answer ...
On the second part I've highlighted, you weren't honest were you?
The TOC has you 'bang to rights' on this. You've admitted the offence and that you've been doing it for an extended period.
They may choose to go straight to prosecution. They may want to explore the matter further perhaps by asking you to attend an interview. If you are (very) lucky they may offer an administrative settlement (not a fine as such) but this would involve the fares avoided (c.£500 ? over 5 months) plus a significant contribution toward their admin costs.
Be very careful or you may further incriminate yourself. And remember - on the issue of what evidence they may, or may not, have on your past behaviour - they know what they have, or don't have. You don't.