It would be legal (albeit immoral) for northern to accept a settlement payment from a customer, then virgin write, threaten prosecution, accept a settlement, BTP to write and threaten prosecution, go through with a prosecution for a byelaw offence, and then me commence a prosecution myself for a RoRA offence. . . . . .
Are you aware of circumstances such as these actually occurring or is this merely hypothetical?
I should hope that any customer faced with those situations would seek appropriate legal advice and repel those prosecutors robustly!
As is so often to be found, many of the answers to questions about the interpretaion and application of railway law were clarified in the early years of the legislation.
This one was the subject of
Noble v Killick (1891) 60 LJMC 61 DC.
Killick refused to pay an excess fare which would have regularised his invalid ticket. The lower Court dismissed the prosecution because having been asked to pay the excess fare, he could not be acted upon criminally. The Company appealled. The Appeal Court held that the Company, having demanded payment of the fare, does not exonerate an offender from criminal liability.
Case remitted for conviction under the Regulation of Railways Act S.5 (2).
That deals with the question of a Criminal liability remaining subject to a prosecution after a civil debt is proposed. I can't think of a case in railway law where multiple parties have accepted civil settlements in lieu of a prosecution for a single incident of an unpaid fare.