Who knows who was alerted and when? Tony Blair was supposedly aware of something going on last week when he appeared with Bush, and I am sure Bush knew about it. The problem was that most people thought the attack was going to be later on in the year. The investigation started many months ago, but in the meantime, thanks to our courts, the US lost the capability to perform the type of surveillance that had enabled us to give the Brits the initial tips to begin with.
Furthermore, I am sure that every intelligence service in the world is afraid to turn any info over to the US, because the info will either be leaked or later used against that country in a US court of law.
Right on there. I believe that has been the general consensus and forecast here @ FR. A sad state of affairs, as we have many good loyal dedicated people working in our agencies but there are some in sensitive areas who think nothing of leaking for their own curious reasons.