Sven Hjerson is the fictional detective created by author Ariadne Oliver. He is Finn and vegetarian. In the first novel of Mrs Oliver featuring him, he was around thirty-five, and at the time of Mrs McGinty's Dead he is 60. Robin Upward wanted to make a stage play about him, and suggested that Sven Hjerson's part could have been played by Cecil Leech.
It seems that the issues that Ariadne was facing about continuing to write about Sven, mirrors those Agatha Christie had about writing about Hercule Poirot.