To redact the information, the background of the associated text in a PDF document was made black. The problem with that is that if somewhere were to copy that information, and then paste it in Notepad, for example, without the formatting, they could read it.
Try it, with the text snippet below. It works the same in a PDF file.
This is top secret.
A secure version of the document has now been published and the MoD said it was working to prevent such an incident happening again (possibly by educating folks on how to properly redact information). The report was published on Parliament’s website after a Freedom Of Information request.
The Daily Star did not publish the information that was accessible, but did note the following highlights of the "secret" paragraphs.
- An expert opinion on exactly how much of a structural failure would be necessary to cause a core meltdown.
- The ability of the U.K. nuclear fleet’s reactors to cope with another potentially catastrophic accident (the type of which, the DS did not detail) is also described as "unacceptable" in the report.
- Ways that American nuclear submarines deal with on-board disasters and how these methods are superior to the U.K. (twice as safe, in fact).
"The MoD is grateful to the journalist for bringing this matter to our attention. As soon as we were told about this, we took steps to ensure the document was removed from the public domain and replaced by a properly redacted version. We take nuclear security very seriously and we are doing everything possible to prevent a recurrence of this."