Re: Card clash detection
But that's not NEARLY enough. Imagine a wallet with an Oyster with a monthly ticket loaded and two contactless debit cards -- not all that unusual a config.
1) Scanner sees all three at the same time -- choose the Oyster.
2) Scanner sees Oyster and card A, the card that purchase the Oyster. Choose the Oyster.
3) Scanner sees card A only. System matches Card A with purchase of single monthly Oyster, choose Oyster -- but see next point.
4) Scanner sees card A only. System matches Card A, card A has purchased a monthly ticket on one Oyster card and topped up a different Oyster card. Should this journey go against the monthly ticket, or the Oyster card presumably carried by a family member or friend?
5) Scanner only sees card B, which has never been used to purchase any Oyster item. Charges can only against B -- or can they go against the monthly Oyster as that has been detected "in the same wallet as card B previously"?