In an essay in the volume As Her Wimsey Took Her, Margaret P. Hannay reports that the creator of Lord Peter Wimsey wrote an unpublished address on "The Craft of Detective Fiction" in which she identified six qualities needed in a fictional sleuth. I quote Hannay:
- The detective must be in a position to be brought into crimes and enabled to work with the police.
- He must be able to drop everything at a moment and go off somewhere to investigate the crime.
- He must be able "to tackle anything from a subtle poisoning to an elaborate alibi produced by mechanical means" if he is to be the hero of a series of books.
- He must have the physical equipment to be able to cope with violent criminals.
- He "must be leisured and rich."
- If he is to figure in a series of books, he should not be too old to start with, he should have some loose ends hanging out to be developed later, and his character should evolve gradually.