I reject the idea that 1 in 8 people travelling on the trains were not paying for their ticket, I do not believe this to be an accurate reflection of the revenues or the nature of the good people of Forest Hill.
What I suspect is that there have been an increasing number of people needing to replace tickets that do not work on these barriers, although they have always worked at London Bridge. The ticket office is now open later in the evening, which may explain a certain increase in ticket sales when people are unable to buy tickets and get a permission to travel ticket.
I would like to see evidence that revenues have increased at Forest Hill Station in the last few weeks and I shall ask Southern Railways to provide such evidence.