> I suppose it would be only the same as credit cards.

The cards seem to accept cash

Warrants aren't all you think they are (this is for the USA, but the UK is not exactly a beacon of liberty in comparison, so I doubt it's much better): https://web.archive.org/web/20140718122350/https://www.popeh...

> But that's within a legal system designed by an elected parliament.

Ah well if it's an elected government then the risk of it turning hostile to its people is zero, of course!

And ask "did that risk materialize?" to the people in China, or North Korea, or Russia, or Belarus, or Germany [1], or USA [2]. There are countless examples of the dangers of surveillance, in the present and in history - you don't need a specific example of exactly Oyster cards being used, to know they are a danger.

[1] https://www.theguardian.com/commentisfree/2025/apr/03/german...

[2] https://www.timesofisrael.com/us-administration-argues-it-ca...