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Polly I destroyed it when I got the new one, middle of last year.
All the usual sites I use for shopping, groceries etc I put the new details on when I received the new card.
But this refund is for a one off purchase of tickets for an opera which they have cancelled, not me, and have refunded to the original card number.
So as nobody really seems sure, I shall wait a few days and see. I have a feeling it will go through without a problem but I may be wrong.
I think Karl's answer is the nearest. I'll let you know what happens. Thank you all. xx