A member of the public made a freedom of information (FoI) request to the police, ‘Could you provide the number of officers at each rank and number of staff at each grade?’ What they received was not only a numerical table but, inadvertently, a huge Excel spreadsheet called ‘the source data, which should never have been released for public scrutiny on an FoI website. It was removed after 2½ - 3 hours once police became aware of it. Each line contains information from the top of the force down - surname and first initial, their rank, grade, where they are based and the unit they work in; including sensitive areas of surveillance and intelligence. The sensitive information exposes many in nationalist communities who were taking great care to keep who they work for a secret, in some cases even from friends and family. The scale of this error is enormous; the consequences cannot be evaluated. It is probably the worst data breach in the organisation's history.