Here's a link to the Web-only editorial the Register did on the thwarted car bombing in London. I was able to talk with Brian M. Jenkins, the noted terrorism analyst at the Rand Corp., and he helped me sort out speculation from what was known at the time, about midday Pacific time.
Things have changed since then as more has been learned. It now seems fairly certain there were two cars rigged to explode, and the plot could be more elaborate. It still looks to me more like the work of relative amateurs more inspired by al-Qaida than directed, but I'm willing to be guided by the facts as they emerge.
Several things seem important. There was virtually no warning, and while it seems quite possible that the device would not have gone off -- it's different building something from an illustration than having actual experience doing it --it may well have been a combination of luck and alertness that prevented a devastating explosion. So it wasn't surveillance and profiling that worked this time, but ordinary police work.
This incident also demonstrates yet again that what the West faces is not a centrally-directed conspiracy emanating from a nation-state but a diffuse web of cells, some freelancing, that is loosely controlled if at all. It should seem obvious (but is it?) that military attacks won't stop them. It should also seem obvious that these attacks will continue as long as the U.S., U.K. and other countries occupy Muslim countries. That occupation is the most effective recruiting tool for the jihadists. Not that all such actions would stop if we pulled out -- indeed, there might be a flurry of them in the months following. But staying virtually ensures they will become a feature of life for years to come.