That’s what contactless cards do now, there’s a PAYG cap. When you read about it doesn’t really sound that complex (not sure if it needed a clever bloke with an algorithm, but then what do I know?)

I guess because they couldn’t work out a way for you to purchase a travel card on your contactless card, so this was the only way to allow regular commuters to use their contactless.

Anyway it was the reason I switched over from oyster to contactless. I realised I was getting ripped off as I would always use PAYG and _sometimes_ went over the caps.