From the BBC:
The documents belonged to a very senior intelligence official working in the Cabinet Office. A passenger on the train from Waterloo in London to Surrey spotted an envelope the papers were in abandoned on a seat and handed the documents to the BBC. A full-scale search for them had been launched by the Metropolitan Police. Just seven pages long but classified as "UK Top Secret", the latest government intelligence assessment on al-Qaeda is so sensitive that every document is numbered and marked "for UK/US/Canadian and Australian eyes only", BBC security correspondent Frank Gardner said. However, it appears that in a serious breach of the rules, according to our correspondent, the document was taken out of Whitehall and left on a train on Tuesday. 'Damning assessment' When a fellow passenger saw the material inside, which included a top-secret and in some places "damning" assessment of Iraq's security forces, they handed it in to the BBC.I think the right term for this situation would be: Gordon Brown has found a fiver - only to find out that he's lost a tenner.