Does this mean that an American in London is going to have trouble using his card?
Not in general. I used the same card in hotels, restaurants, stores, tourist attractions, taxis and buses, etc. with no problem, both before and after the train incident.
In a store, no, as the start date is something you never get asked for. Even in telephone transactions it is never asked for. And this is the first website that I have come across to ask for the date. On the form the 'date valid to' field is marked as mandatory, but not the 'date valid from'.
Both fields were shown as mandatory, if I recall correctly. Regardless of how they were marked, it wouldn't let me proceed without the issue date field. It specifically flagged it as "missing".
I've just made a successful transaction on GWR leaving the 'date from' field blank. I wasn't expecting it to go through (it was a ticket I didn't need)- I should have been prompted for a pin code from my bank by text as always, always happens- but it went through. Glad I chose the cheapest possible ticket from my station.
Sorry if my post caused you to waste some money. I don't understand how you got it to work though, unless they've revised the process. Maybe they had some complaints about this very issue and reconsidered?
So what may have stopped the OP was the CV number on the back of the card (bottom right field of the screen) or the OP's bank was suspicious.
Nope. I checked everything four times, and my wife went over it two more. I also doubt it was the bank because I used the same card uneventfully for a week before and after.
PS- None of my cards are Maestro or Switch, just normal cards.
Mine was a standard CapitalOne Mastercard. I've been using it for over a decade, including twice in the UK and last year in Italy, with no problem.
Alas, a mystery probably never to be solved. Thanks all for weighing in!