Mark was born in Chorlton-cum-Hardy, a suburb of Manchester, the youngest of five children of a prosperous mantle manufacturer originally from Yorkshire.

[1] When he left school in 1935[2] he got a job as a carpet salesman, but finding this boring,[3] in 1937 he joined Manchester City Police as a constable, much to the dismay of his father, who considered it beneath him and said becoming a policeman was only one step above going to prison.

Mark recalled a test for claustrophobia which involved being tipped down a 45-degree drainpipe into a pitch black chamber with two false and one actual exit.

[3] He applied for the post of Assistant Chief Constable of Newcastle upon Tyne, but was unsuccessful and instead enrolled on the senior command course at the National Police College.

[1] Following the 1966 escape of the spy George Blake from Wormwood Scrubs, Mark was appointed to the Mountbatten inquiry into prison security.

Here he attracted the attention of Home Secretary Roy Jenkins,[3] and in February 1967 was appointed Assistant Commissioner "D" (Personnel and Training) of the Metropolitan Police,[7] where his welcome was less than ecstatic from a force that did not like outsiders;[1] at the end of his first week, he was encouraged by Commissioner Sir Joseph Simpson to apply for the post of Chief Constable of Lancashire.

Peter Brodie, Assistant Commissioner "C" (Crime), was widely tipped to succeed him, but Home Secretary James Callaghan saw the opportunity to impose government will on the force and offered the job to Mark.

In 1971, with Brodie, an old-school officer who commanded CID, out of the country, Mark formed A10, a special unit established to investigate corruption.

[1][8] Brodie took early retirement the day before and was replaced by Assistant Commissioner "B" Colin Woods, who had never previously served in CID.

In the late 1970s, he appeared in television adverts for Goodyear tyres and his "I'm convinced they're a major contribution to road safety" became a widely used catchphrase.