The programme was originally intended to appeal to a family audience as an educational programme using time travel as a means to explore scientific ideas and famous moments in history. On 31 July 1963, Whitaker commissioned Terry Nation to write a story under the title The Mutants. As originally written, the Daleks and Thals were the victims of an alien neutron bomb attack but Nation later dropped the aliens and made the Daleks the aggressors. When the script was presented to Newman and Wilson it was immediately rejected as the programme was not permitted to contain any "bug-eyed monsters". According to producer Verity Lambert; "We didn't have a lot of choice — we only had the Dalek serial to go . . . We had a bit of a crisis of confidence because Donald [Wilson] was so adamant that we shouldn't make it. Had we had anything else ready we would have made that. " Nation's script became the second Doctor Who serial – The Daleks (also known as The Mutants). The serial introduced the eponymous aliens that would become the series' most popular monsters, and was responsible for the BBC's first merchandising boom.