Patrick Petrella is a police detective created by the British mystery writer Michael Gilbert who appears in ten books published between 1959 and 2003 and is probably the best-known of the half-dozen or so recurring characters that Gilbert wrote about throughout his long career. He is the protagonist of two novels and of 54 short stories that were first published in magazines and newspapers and then republished in eight collections of stories. In one of the short stories, however, "The Spoilers", in Game Without Rules, featuring Mr. Calder and Mr. Behrens as the protagonists, he appears only very briefly, at the end of the story. In his first appearance in a novel, the 1959 police procedural Blood and Judgement, Petrella is a "probationary" Detective Sergeant at the (fictional) Q Division of the London Metropolitan Police. By the final novel in the series, Roller Coaster, he has worked his way up to become a Superintendent.
Gilbert attributes reading the poem Who Has Seen The Wind? by Christina Rossetti during a boring church sermon as the inspiration for the first Petrella mystery. The lines "But when the leaves hang trembling, the wind is passing through" caused Gilbert to suddenly visualize a young policeman "who read and could quote poetry" visiting a working class family who are trembling and uncommunicative because the father, an escaped convict, is hiding in the kitchen, and the policeman suddenly realizes why.
As his name indicates, Petrella is the offspring of different nationalities. His father, Lieutenant of Police Gregorio Petrella, was in the Spanish equivalent of England's Special Branch when he met Petrella's British mother, Mirabel Trentham-Foster, in front of the pyramids in Egypt. Lieutenant Petrella, whose primary job was to prevent Spain's dictator, Francisco Franco, from assassination, spoke a number of languages and was often sent abroad to investigate possible conspiracies against Franco. On one of these missions he met Miss Trentham-Foster, who was sketching the pyramids. She was the daughter of an English architect and the grand-daughter of a judge "who was also an accomplished painter." Patrick spent the first seven years of his life running around with great freedom with other Spanish boys his own age. On his eighth birthday, however, his mother "put her small foot down" and began the process that would launch him "into the traditional educational system of the English middle and upper class." So he spent the next nine years at English boarding schools. At the age of 17 his father, by now a Colonel, sent him to the American University in Beirut, where he learned to speak Arabic, then to another "rather peculiar" one in Cairo, where, among other things, he learned to pick locks. His ambition had always been to be a policeman; on his 21st birthday he joined the Metropolitan Police as a Constable. After training, he was first posted to the North London Division of Highside.