UK bank details sold in Nigeria

According to BBC, fraudsters have been selling personal information of Britons that was stored on recycled hard drives.
http://news.bbc.co.uk/1/hi/business/4790293.stm

Owen Roberts, an anti-fraud expert, was quoted saying that deleting files isn’t enough.
What about encrypting sensitive data – and keeping it encrypted after you “delete” the file, so it will remain inaccessible for life?