South African-born Stratford Johns was forever associated with the role of tough, abrasive Superintendant Charlie Barlow on TV's Z Cars (1962) and its sequels Softly Softly: Task Force (1969) and Barlow at Large (1971). In between, he also played Barlow in the miniseries Jack the Ripper (1973) (which, in turn, led to a 'cold case' investigation series called Second Verdict (1976)). He even spoofed his famous screen detective on The Two Ronnies (1971). His perennial sidekick was the actor Frank Windsor (in the role of Sergeant Watt), who once jokingly referred to their on-screen partnership as being "the Morecambe & Wise of serious television".

Johns was educated in Pietermaritzburg in Natal Province. He began working life as a deckhand with the South African Navy during World War II. He then had a brief spell as an accountant, before finding his vocation in the dramatic arts. After some work in local repertory companies, he went to England on a one-way ticket in 1948, acting for four and a half years on stage in Southend-on-Sea, followed by a comedy act in the variety halls. Since this amounted to little more than a meager income, Johns was forced to make ends meet by doing handyman jobs, building fences, painting and gardening. His big break came in 1962, when he was presented with the choice of whether to accept a small part in the epic blockbuster Cleopatra (1963), or, alternatively, screen test for a new BBC police series (initially called "Crime Cars"). Though tempted by the gentler Roman climate, he wisely chose the latter.

For better or worse, Johns became identified with Barlow to such an extent over the years, that he was even sought-after by police for recruitment drives on television. Conversely, though he occasionally attempted to break away from typecasting, especially on stage, he was rarely deemed to have succeeded.