John Dickson Carr
John Dickson Carr was an American who moved to Britain in the thirties and became an overly prolific writer of gentleman sleuth type "cosy crime" mysteries. He sold so many he was compelled to split himself in two, giving off an alternate persona as Carter Dixon, a rather transparent ruse unworthy of the convoluted and unlikely twists his tales hang on.
Carr/Dixon's big thing was the impossible crime or locked-room mystery. He focussed on it obsessively, autistically, to the exclusion of all else. Probably only half of his plots would have any kind of chance of being enacted in reality, so prospective murderers need not look to him for pointers: in one book he has his lead detective proclaim, "We are not concerned with whether the thing would be done, only if it could be done." But even given the occasional disappointing denouement, there is much to commend this oddball.