According to
Juan Cole's sources, the British only infromed their U.S. counterparts of some details known to them only two weeks ago, to avoid premature disclosure of the plot:
US authorities were only told about some details two weeks ago, apparently. It may be that the British counter-terrorism community learned its lesson from the loose lips of the Bushies in summer of 2004. I argued then that from what we could tell from open sources, it seemed likely that the Bush administration played politics with information about a double agent in Pakistan who was helping monitor a London al-Qaeda cell. It seems likely that the election-year leak allowed budding terrorists like Mohammad Sadique Khan to escape closer scrutiny, and so permitted the 7/7/05 London subway bombings to go forward.
What if the timing of yesterday's crackdown/arrests was driven not (or not only) by the impending "dry run". Instead, could it be that the Brits noticed the re-emergence of Cheney from a few weeks' hiatus and opening a political terrorism-related tirade at the Democrats?
We will probably learn the actual sequence from the Brits in a short while. But it is sad that this sounds even remotely plausible.