Agreed, C-Flat. Conclusive proof? My arse!
If Pitcairn was facing a massive military invasion by a US-led force, I imagine Osama would be pledging full support to the people of Pitcairn.
As for the authenticity of the tape - it's probably genuie, but when was it made? On it Osama refers to the attack on Tora Bora last year. Oops, that was in 2001, two years ago.
Colin Powell seems to have read a transcript before Al Jazeera even broadcast the tape - Al Jazeera is an independent station that would not knowingly pass material on to a country seen by most of its viewers as hostile. So how long has this cassette banged around in diplomatic bags and boxes before being passed to Al Jazeera, and what route did it take to get there?
However, it does play nicely in the light of Powell's desperate attempts to prove a link between Iraq and Al Queda.
You have the world's number one bogeyman pledging support for the world's number one (or is that two, or even three) hated nation. If you're a little dim and like your facts served up in sugar frosted sound-bites by an uncritical media, it's convincing. Hell, it's all the proof we need. Let the tanks roll!!!

As for the tanks at Heathrow, I wonder what use the Scorpion would have been if things had gone pear-shaped? A 76mm rapid-fire cannon seems a little OTT. It wouldn't surprise me if the shells had been left behind just in case some eejit ballsed up. Made good telly, though, and may have deterred a loon from doing something unpleasant.