"There is no principle of law that knowledge in a prosecutor begins immediately any employee of that prosecutor has the relevant knowledge, and Donnachie does not establish one. It is right that prosecutors are not entitled to shuffle papers between officers or sit on information so as to extend a time limit. There is, however, a degree of judgment involved in bringing a prosecution, and knowledge, in my judgment, involves an opportunity for those with appropriate skills to consider whether there is sufficient information to justify a prosecution."