Two years ago, a hostile Prime Minister launched the Monochrome inquiry, investigating "historical over-reaching" by the British Secret Service. Monochrome's mission was to ferret out any hint of misconduct by any MI5 officer — and allowed Griselda Fleet and Malcolm Kyle, the two civil servants seconded to the project, unfettered access to any and all confidential information in the Service archives in order to do so. But MI5's formidable First Desk did not become Britain's top spy by accident, and she has successfully thwarted the inquiry at every turn. Now…