Good luck finding out ahead of time whether your foreign card is going to be accepted by the system.
Also seems difficult for children who don't generally have credit cards.
Also seems difficult for children who don't generally have credit cards.
On the tills themselves there's all the signs of all the accepted cards and it was a fairly exhaustive list. It's also probably available online, so it should be pretty easy to check ahead of time.
American Express (AMEX) MasterCard and Maestro (some cards issued in the USA, Canada and the Netherlands aren't accepted) Visa and V PAY (some cards issued outside the UK aren't accepted)"
So no you can't tell ahead of time.
Although to get the child rate (half price) you need to show ID (if it's not obvious) and get the native Oyster card.