I seem to recall foreign exchange was involved and the decimal point ended up in the wrong place. He ended up in Spain with the money. There was court action, but jurisdictional issues. I think they compromised. I don't remember it being all that clear that (as Theo suggests) the bank was in the wrong and was not entitled to reclaim the money.
I'd be very wary of going down the legal road. The larger the amount involved the more expensive the legal fees and hassle as the bank surely won't want to roll over. Besides, "in the course of justice, none of us should seek salvation".