The last time the British Government was quite to riled up was over the Spycatcher saga, when a former British spy published his memoirs of an organization that (at that time) didn't even officially exist.
On that basis, do I believe this story likely? Yes. Do I believe this to be the whole story? No. The gagging order covers not only the story leaked, but anything and everything else in the memo, implying that there were other, far more damaging, elements in there.
Do I believe this was a joke? No. Ronald Regan's infamous snafu on radio, where he said that he was going to bomb Russia - that was a joke. Caused a bit of a stink, too. But nobody was arrested for the broadcast, no secrecy order was placed, it was business as usual and the incident largely forgotten.
Do I believe Al-Jazeera are a "legitimate target"? When people start talking in those terms, they sound like the IRA at the height of their bombing campaign. You can't just go around labelling things "legitimate targets" because you happen to feel like bombing them. Well, I guess if you're the world's only superpower, you can do what the hell you like, but it doesn't make it lawful and it doesn't make it right.
But what of all the propoganda? What of it? It'll exist, whether Al-Jazeera exists or not. To abuse a quote beloved of gun nuts, if you criminalize information, then only criminals will have information. You don't change anything, except negatively.
There is another factor to consider, and that is truth in the media. The Pentagon has, in the past, openly considered making false statements through the media and fabricating news. All Western journalists are embedded in the US military, see what the US military want them to see, and report only what the US military want them to say. Those who have reported anything different have been subject to retribution. (And, yes, that has happened.)
There are no Western media outlets willing to risk getting their reporters killed, by operating outside of those restrictions. (At least one reporter, from ITN, who was embedded with the Iraqi army during the initial invasion was killed by US forces, despite being clearly marked - or, possibly for that reason. It's doubtful anything will be acknowledged by the Pentagon for another 50-75 years, if that was the case.)
This leaves the middle-eastern journalists to do any investigative reporting. No, I don't advise trusting them to be impartial or even honest, but the fact of the matter is that there is nobody else who is willing to risk saying anything that might conflict with American official statements.
It is highly significant that the ONLY disciplinary proceedings that have taken place have done so after proof of corruption and abuse within the armed services has been published. Not before. From the bodies burned in Afghanistan to the Abu Gharib fiasco, the dominant response has been to pacify American sentiment. The military knew of many of the cases of abuse years before they were reported in the press, and did nothing.
Hate them or loath them, Al-Jazeera are vital in keeping the pressure on the military, to prevent far worse attrocities. If no media were present, Iraq would be no different from Darfur. In some ways, that might be a pity - societies change very reluctantly and only in extreme situations. At the relatively low levels of reported corruption, there won't be anything like the backlash needed to root out the degenerates who support and encourage war crimes.
The real tragedy is that, no matter what GWB said to Blair, it simply isn't going to be bad enough to force people to face up to their ethical responsibilities. Nothing in this war has. All the sides involved have seriously sick, twisted, evil minds but few - if any - will ever be called on it, and those who are will do so as fall-guys in evidence-tree trials of the kind we've been seeing.
There is nothing anyone can do - or should do - other than press on for the defence and the freedom of journalists of all nations and all sides. Truth - whatever scraps we can salvage - is the only safeguard. That is the only weapon that this kind of evil cannot endure. Anything else will just feed it.