These are typically stations that are outside of London. If you reach the destination station, you'd probably need to appeal to the kindness of staff members who attend the ticket barrier (if there is one), who might ask someone to buy a ticket or pay a penalty fare. But it's functionally equivalent to traveling without a ticket at all.
You'd also have to pay a default charge for an incomplete journey on the PAYG ticket, but you could potentially appeal to have this reversed.
It's usually made pretty clear on train announcements that you're leaving the contactless PAYG fare zone.
> Meta said it has cooperated with regulators and pointed to its announced plans to give Europeans the opportunity to consent to data collection and, later this month, to offer an ad-free subscription service in Europe that will cost 9.99 euros ($10.59) a month for access to all its products
> Tobias Judin, head of the international section at the Norwegian Data Protection Authority, said Meta's proposed steps likely won't meet European legal standards. For instance, he said, consent would have to be freely given, which wouldn't be the case if existing users had to choose between giving up their privacy rights or paying a financial penalty in the form of a subscription.