Markstein was born in Berlin in Germany, but emigrated with his family to England with the rise of the Nazis. It is rumored that in the 1950s he had worked in British intelligence but there is no historical basis for this, before becoming a journalist for the military tabloid The Overseas Weekly whose U.S. G.I. readership referred to the paper as The Over Sexed Weekly due to its scandal driven content as noted by Time magazine. The masthead of the newspaper lists him as head of the London desk.
He moved into television, first on the factual series This Week, before acting as story consultant and contributing to multiple episodes of ITC's Court Martial (1966), and then joining Danger Man as story consultant for the last black-and-white episode (1966), then story editor for the two episodes which were made in colour (1967). Around this time he also wrote four episodes for Rediffusion's children's drama series Send Foster (1967), and worked on the script for Peter Yates's Robbery (1967), a fictionalised feature film based on the 1963 Great Train Robbery.
When Patrick McGoohan announced his decision to leave Danger Man, Markstein edited the basic ideas that McGoohan had worked on since 1962 that became the British cult classic series The Prisoner, created by, starring and often written and/or directed by McGoohan. Together with producer David Tomblin and the star McGoohan (uncredited), Markstein co-wrote the first story "Arrival," and then settled in as script editor for the series. He later described the job of story editor as "the key man in any series, he is the man in whose hands is the ethos of the series, the spirit of the series, and it is his job to cast the writers and the authors the way a director casts the actors and the stars".
Markstein actually makes a fleeting appearance at the start of almost every episode of The Prisoner - as the balding, bespectacled 'man behind the desk', to whom McGoohan's character is seen angrily handing his letter of resignation; and played the same, non-speaking character in the episode "Many Happy Returns."
Markstein's view of the series was for a more-or-less conventional action/espionage story. However as McGoohan controlled the series as Executive Producer and owner of Everyman Films, Markstein became increasingly dissatisfied as an employee and ultimately left the series after the conclusion of the initial block of thirteen episodes. A glimpse of Markstein's face remained in the opening credits, but it was without him that McGoohan took the series to its most surreal and existential levels in the final four episodes, and its bizarre conclusion.
1970s—80s
After The Prisoner, Markstein went to the newly merged Thames Television, initially as an in-house script editor, then as story editor for the first series of a new counter-espionage drama Special Branch (1969); the third and final fourth series of spy drama Callan (1970, 1972); several episodes of Armchair Theatre (1969, 1971); and the first series of The Rivals of Sherlock Holmes (1971). He also acted as producer for the first series of Man at the Top (1970—71), a continuation of the story begun with John Braine's 1957 Room at the Top. Markstein became Thames's Head of Script Development, where he had input into the development of the 1974 Armchair Cinema season made by Thames's new all-film Euston Films production unit, including one-off drama Regan and its celebrated successor series The Sweeney.
In 1974 Markstein again went freelance, and co-wrote the screenplay for The Odessa File, based on the novel by Frederick Forsyth. In the same year, together with Jacqui Lyons, he co-founded the literary agency, Marjacq Scripts Ltd, initially to represent screenwriters, later also thriller writers and computer game authors. The name is a derived from Markstein's surname and Jacqui's forename.
In addition to his interests in Marjacq, Markstein also wrote a number of thrillers, including The Cooler (1974), The Man From Yesterday (1976), Chance Awakening (1977), the historical epic Tara Kane (1978), Goering Testament (1978), Traitor for a Cause (1979), Ultimate Issue (1981), "Ferret" (1983), and Soul Hunters (1987).
He continued to write for television, including working on two series of Shades of Greene (1975—76) for Thames, a series of adaptations of short stories by Graham Greene, for which Markstein acted as script consultant jointly with Greene's brother, former director-general of the BBC, Sir Hugh Carleton Greene. Other series he wrote episodes for included Return of the Saint (1978), the pilot (Storyboard: The Traitor) and two episodes of Mr Palfrey of Westminster (Thames, 1983, 1984, 1985), and one episode of Philip Marlowe, Private Eye (Thames, 1986). His final television work was as story editor on the six part series London Embassy (Thames, 1987), based on a book of short stories by Paul Theroux about the unusual experiences of an American diplomat based in London.
For the cinema he wrote the initial synopsis for the 1982 SAS embassy-storming film Who Dares Wins, which was then turned into a novel The Tiptoe Boys in thirty days flat by author James Follett and then into a screenplay by veteran screenwriter Reginald Rose. James Follett, who began writing professionally in 1973, has described George Markstein as his "guru", and is still represented by Markstein's company Marjacq.
Markstein died in 1987, of kidney failure, following a long illness.
