Just happened upon this, a year or two old: a ‘Critical Look at Britain’s Spy Machinery’, in particular the circumstances that led to the production of the infamous September Dossier. The author identifies gradual, structural changes at the SIS as responsible, specifically the gradual diminution of the role of the ‘Requirements’ side of the organisation, responsible for evaluating intelligence provided by the ‘Production’ side.
It’s a quick read, touching upon the Butler Report and the history of the SIS. The author, Philip Davies, differs from Lord Butler in his assessment of the structural causes behind the cock-up:
This failure has to be seen not as a short-term breakdown in the SIS validation machinery resulting from cutbacks in the 1990s, as Butler contends, but as the culmination of a steady weakening of the Requirements mechanism for handling tasking, dissemination, and validation, since 1974.
Davies agrees with Butler on the main weakness of SIS intelligence: the reliance on second-hand information relayed by their principal Iraqi souces.
Thus, all four of SIS’s main sources prior to the war proved to be reliable overall; the problem with this stable of agents was not wholesale inaccuracy, but rather hearsay reporting by one and reporting on behalf of an unre, liable subagent on the part of another.
This is interesting, and echoes much post-Butler reporting. I am no Jack Ryan, but it is not clear to me why second-hand reports are necessarily worthless. Put another way, they probably contain some information. Given that, how many such reports does one need in order to be convinced?
One suspects the intelligence officer is more artist than scientist, and as such is more difficult to criticise ex post. The same might be said for the UK’s Joint Intelligence Committee.
P.S. That said, here‘s a call for the US intelligence services to go all Moneyball. This book has a similar message, but is mostly of interest thanks to the single, unintentionally poignant review from the author’s dad.