Exposed: Barclays account details for sale as 'gold mine' of up to 27,000 files is leaked in worst breach of bank data EVER
- Cache of personal and financial details stolen and sold to rogue traders
- Unscrupulous dealers 'used information to pressure investors into scams'
- Bank thanked Mail on Sunday for revelation and launched investigation
- Barclays now face unlimited fines for not protecting customer information
- Former City broker blew the whistle on the files to stop problem growing