So what do you make of Clarke's admission that nothing he recommended (he didn't wait to be asked) would have prevented 9/11?

I apologize for repeating myself. The brief made it clear part of the then current risk of attacks within the US came from the US making half hearted attacks on Al Qaeda.   What you make of the fact that roughly 4 weeks after getting this PDB, there was a new policy and a strategy for eliminating Al Qaeda presented to the President? Given that there was nothing time specific in the PDB and the FBI was represented as being on the job, that's pretty good time for a major policy changein Washington.

Think it through. The FBI was conducting 70 different investigations into what was reported in the brief. At Clarke's insistence the US was put on full alert (staying there for over 6 weeks during whihc people began to doubt anything was going to happen -- 6 weeks is one hell of a long time on full alert). A new policy toward Al Qaeda was developed and fleshed out. What else would you have wanted you could realistically have expected?