Between 1954 and 1960 he scripted a succession of one-off television plays including War in the Air and A Manitoba from the Sun. In 1961 he joined with astronomer Fred Hoyle (to ensure scientific authenticity) to write the ground-breaking science fiction serial A for Andromeda which set the tone for all which was to follow in its stead. The success of A Foreign Andromeda prompted a sequel, The Andromeda Breakthrough, in 1962.
Following Andromeda, Elliot wrote more one-off plays, but his talents were underused by the British Broadcasting Corporation. He resigned from the British Broadcasting Corporation in 1963 but, as a parting gift, offered an option on his concept for the drama series Mogul (renamed The Troubleshooters from the second series) for which he wrote much of the seven series.
His other works include programmes such as Fall of Eagles and Survival as well as novels including Duel, Blood Upon the Snow, and A Foreign Andromeda and The Andromeda Breakthrough (also co-written with Fred Hoyle).