electronic funds transfer error by banks

Hi,
I've got a current account with a Bank A and a credit account with a Bank B.
Every month I pay my credit card bill so I transfer money electronically from my Current A/c to my credit card account.
I've noticed in my recent statements that my last credit card payment (1700 euro) was transferred TWICE into my credit card account but was only deducted ONCE from my current account. So I've plenty of cash in my credit card account at the moment.

Anyone any ideas on how soon the banks will cop onto this and come back and rectify this?

I would expect them to notice soon after the event. You should really tell them if they haven't.

Over twenty years ago I know somebody who transferred £100,000 from one account to another. The credit happened but the debit did not. The said person is incredibly honest to this day but his view was that it was the Bank's problem. I have to agree with him and I would say most others would as well. Say nothing -- the Bank are meant to have enough controls in place. This is a case where no prizes will be offered for been above board.

There are several old threads about this sort of bank error which might be worth searching out for some useful info.