An early television credit was an episode of Doctor Finlay’s Casebook (1967) called The Forgotten Enemy. At about the same time he formed a writing partnership with Henry Lincoln, and together they were the authors of three 1960s Doctor Who stories during the Patrick Troughton years: The Abominable Snowmen, The Web of Fear and The Dominators. These scripts created two enduring monsters, the Yeti and the Quarks. The latter script was their last contribution to the programme and, after disagreements with the production office, it was cut by an episode and credited to the pseudonym Norman Ashby. Haisman and Lincoln also worked together on episodes of Emergency Ward 10, but their writing partnership was not long lived.

Haisman also wrote for many British television shows including The Onedin Line (on which he also worked as script editor), Howards' Way, and Swallows and Amazons Forever!; and on the horror movie Curse of the Crimson Altar, also known as The Crimson Cult (1968), again with Henry Lincoln.