80% of other passenger will have paid extra to do this route
?!!
No sane passenger would go by this route! Only an enthusiast scratching off a new route would want to do it.
They will probably in the end be paying for your ticket becasue of fare rises
Why/how is this the case? Enthusiasts have been doing routes by longer journeys than a "normal" would take for decades, just to experience the route. This does not cost anyone anything. If it did, Rovers would not exist.
Now, I am not defending the OP using this route, I have already told him what he should do. But saying that if the OP takes a longer route it will cause fare rises is just plain daft. Let's keep things in perspective!
so they can install barries to stop people like you





If you replaced checks by guards with barriers, it would open the door to all sorts of utterly bizarre routes and no-one would stop you.
So, in fact, the
opposite of what you say is true!
Given that the OP isn't trying to find a cheaper fare for a journey to Peterborough and only wishes to go a longer route, he would not exit any barriers. Barriers would not stop him. If an Oyster-style smart card approach was adopted across the National Rail network his journey would, in fact, effectively be valid, provided it did not go over whatever the time limit is.
Faredodging, not much different
Something that isn't even punishable by a PF can hardly be compared to dodging. There is no offence committed unless the OP refuses to pay an appropriate excess. I'd be shocked if he managed to do this journey without being charged an excess, and I suspect he'd be asked for more money than if he bought a valid ticket in the first place. So he is daft if he refuses the advice. But just daft, not a criminal as you suggest, and he isn't going to cause fare rises by choosing to take a longer route.