Downing Street identifies leaker with the old "send everyone a different memo" trick

Andrew Lewer, a Conservative Party Member of Parliament in the UK, was today fired from his position in the Home Office after being identified as the source of a leak. To figure out who forwarded internal communications to the political blog Guido Fawkes, they added unique features to each recipient's copy.

In an attempt to try and identify the culprit, a number of MPs were sent the same letter but with slightly different wording in each version. … Mr Lewer is understood to have been dismissed as an aide to policing minister Kit Malthouse after an image of the letter ended up on the Guido Fawkes political website on Thursday. … The letter, which was sent to all ministerial aides, had warned that the prime minister's foreword to the ministerial code "strictly prohibits" leaking, adding: "Please keep this in the forefront of your mind; the position you hold is a privilege and not a right." In what has been described as an attempted "canary trap", it is understood to have contained minor but distinct differences in language in the versions sent to each recipient.

In a fitting irony that should have screamed "trap!" to the recipients, the leaked memo was an order not to leak memos.

A lesson learned by many of us in a decade or so of heightened whistleblower coverage: don't generally publish the stuff leaked to you. Don't even quote it verbatim. Instead, describe it accurately in your own words and treat it as evidentiary material that proves the accuracy of your reportage.