The Bellman was the leader of Jurisfiction, a job held by several people during the course of the Thursday Next series. At first it was held by the character called The Bellman, although his name was just a coincidence. He was succeeded by Thursday Next, who was said to be the best Bellman ever and did the job for two and a half years, before handing it on to Trafford Bradshaw.
The job consisted of running Jurisfiction, and, according to Thursday in Something Rotten, doing a lot of paperwork.