“When the genius fucks up, that’s when I step in,” she told me.

Her workplace was an insignificant nook of Scotland Yard, hidden between the broom closet and the exit sign. It contained an ugly grey desk, a dial telephone, an early nineties computer and a wall of dusty filing cabinets. For 23 years she had been the Yard’s best kept secret. Now, she was about to blow the lid off its most famous consulting detective.

“There was one instance where he looked two seconds at the crime scene and he knew who the culprit was,” she said. “Of course he had also entered the premises without a warrant, placed his foot in the pool of blood on the floor and spilt the potato chips he happened to be eating all over the crime scene.”

She was the one who cleaned up the resulting judicial mess. Antedating warrants, doctoring crime…