Jonathan Morris wrote:

Even after the £20 introduction last year, a gripper 'caught' a guy in
a suit that had £20 in his hand and gave it over before the inspector
said a word. He'd clearly worked out that it was cheaper than a ticket
every day. Sadly, he's right to think it.

On the main line, that should be 20 quid or twice the full single fare
for the journey made. For some commuters into London that is likely to
take it well over that.

It's a good point, though. I'd like to see it increase to the level of
a parking fine, as the amount evaded is usually of a similar magnitude.
60 quid standard, discounted to 30 quid if paid on the spot/within one
month, increased to 90 quid if left too long, would be a good start.
TOCs do like prosecuting people instead of late, but that they have to
resort to this is IMO showing the failure of the penalty fare.

Neil