The notion of bringing Professor Quatermass back for a fourth adventure dated back to at least 1965 when producer Irene Shubik asked Kneale to contribute a new "Quatermass" story for the first season of the science fiction anthology series, "Out of the Unknown". Nothing came of this but the prospect of "Quatermass" making a reappearance arose again when, following the success of the film version of "Quatermass and the Pit" in 1967, Hammer announced it was in discussions with Kneale for a new "Quatermass" adventure. Again, this did not progress beyond the initial negotiation stage. In the meantime Kneale had been coaxed back to the BBC, writing plays such as "The Year of the Sex Olympics" (1968), "Wine of India" (1970) and "The Stone Tape" (1972). Following completion of "The Stone Tape", Kneale was commissioned on 21 November 1972 by BBC head of drama serials, Ronnie Marsh, to write a new four-part Quatermass serial.