Re: a national newspaper, which recorded the data
If there were documents marked RESTRICTED or CONFIDENTIAL, as reported, then by definition it's an offence under the Official Secrets Act to have a copy unless you're an authorised person. The newspaper would have known this, but their lawyers probably told them that they estimated that the Crown Prosecution Service would not consider a prosecution to be in the public interest. I very much hope that they also stored their copies on disposable hardware: the security authorities might otherwise demand cleansing of their server networks. Look what happened to the Guardian's hard disks.