Sam Hamm is the screenwriter who wrote the initial screenplay for Batman. Due to a writers strike, he was unable to present in London when the film went into production. Warren Skaaren and English playwright Jonathan Gems were brought on for re-writes at this time.
Hamm has indicated unhappiness with some changes made to story during the London shoot, like Joker killing Bruce Wayne's parents and Alfred letting Vicki into the Batcave. Hamm also wrote a unused screenplay for Batman II, and still receives "story" credit in the final film for presumably legal reasons.