London Express Transit
Apple Pay Express Transit was recently tested in New York City, and in the future it will be coming to London. You can already use Apple Pay for London’s subways, trains, and buses, but it requires authentication. Express Transit doesn’t require authentication, you just hold it near the wireless pad.
The current stored value card used with Transport for London is Oyster, although it was updated to use any contactless payment card. Stored value cards are ones where you load money onto it. Apple’s Express Transit added support for EMV cards in iOS 12.3.