The amount of people here "illegally" already they haven't a clue, allegedly.
We are an island after all.
What's difficult to stop and check ?
If you got no issues then you have nothing to worry about ?,simple! :scratchhead:
Even cheap just dab your contactless debit card on entry and exit tube gates.
Often The Oyster card is set at a certain price and unless your using it to the max often cheaper way we found on recent recently.