TIL normally do offer an out of court settlement (we saw them offer one last week when someone was travelling with an Advance ticket on the wrong train) but it often takes 2 or 3 letters.
I would write a short, concide letter and see what they say. I suggest you post a draft in this thread so we can proof read it for you.
Thanks Hadders, following advice further up this thread I've tried to focus on the apology, remorse and lessons learned rather than getting in to detail about the offence.
Below is redacted version of what I've drafted today, any feedback is of course much appreciated
Further to my initial letter, I would like to once more offer my sincere apologies for not being in possession of a valid ticket prior to my journey between Lydney and Cardiff Central on Saturday 15th March, an uncharacteristic decision which I am embarrassed and ashamed of
From a personal perspective, this experience has been particularly difficult and sobering, one which has reinforced the responsibilities incumbent upon me as a rail passenger. It is of deep personal regret that it has taken this situation for me to be fully aware of these and this is an experience I never wish to repeat.
I am fully mindful of the severity of this situation and the significant consequences that could follow should I be convicted of an offence within the magistrate's court. I understand that beyond personal repercussions, my actions have adversely affected Transport for Wales, which in turn also impacts fellow passengers for this I am very sorry.
Owing to the severity of the situation I understand that a summons may now be issued; however, I would once again like to formally offer to pay any outstanding sum to avoid this action being taken and reassure you that for any future travel, I will always possess a valid ticket in advance and assure you that I will never place myself in this position again.
Should it be possible to resolve this matter without a summons being issued I would be extremely grateful and I can assure you that I will promptly pay any and all outstanding costs incurred.
Once again, I would like to apologise and I appreciate your time in reviewing my response.