From a recent BBC piece:

“On three occasions I questioned [former MI-6 head] Richard Dearlove about the provenance of this intelligence,” says the then foreign secretary, Jack Straw. “I just had an uneasy feeling about it. But Dearlove assured me on each occasion that these agents were reliable.” However, Mr Straw says that it is ultimately for politicians to take responsibility, because they make the final decisions.

Asked if he looks back on Iraq as an intelligence failure, Sir Richard’s answer is simple: “No.” He still believes Iraq had some kind of weapons programme and that elements may have been moved over the border to Syria.