If you are the man who lost a purple NatWest VISA debit card on Dartmouth Road, I just thought I would let you know I rang the bank and they cancelled it for you. I didn’t realise they’d cancel without warning you (so sorry about that!) but I thought it was safer to deal with it that way.
Someone left a bank card in Crofton Park library once. I rang the bank concerned as we were worried about it being left & they cancelled it straightaway. Think that’s the best thing to do, especially if it’s a contactless card.
I’d agree that if you have a duty of care over the lost property, ringing the bank to cancel the card is best for you and the person who lost the card.
If you are unwilling or unable to ring the bank, destroying the card would be a second best option. The card belongs to the bank, not the account holder, and I am sure that banks do not want lost debit cards being held by third parties. Keeping the card in a non-secure location in case the card holder returns is the worst option.