My first thought? "My gosh, MI-5 has come to life."
Followed by a certain amount of shame, and by the fear that this will be seen as somehow America's fault. In a way, I suppose, it might be: Britain has been one of the few nations supporting us during this whole thing, and it's not a stretch to imagine London being targeted in retaliation.
I hate this. The reporters kept dragging up the "war on terror" phrase again, which I think is something of a misnomer. If this is a war, it's an unwinnable one. Honestly, I think might be partly why Bush went ahead with the war in Iraq. It's an attempt to find the people behind all this shit, and confront them directly. We can't be sure when they'll strike or who they'll victimize unless we have engaged them in warfare. It's an attempt to control the kind of damage they can do.
It may not be working, but at least we're not sitting on our butts waiting to be bombed.
My prayers are with everyone in the UK, and particularly London.