After a whole season of Mel as The Doctor's companion, Bonnie Langford had decided that she did not want to be Mel anymore. She feared typecasting (which, as it turns out, was an entirely founded claim) and wanted to move on. It probably didn't help that Mel is [unfairly] hated by vast majorities of Doctor Who fandom despite Langford being actually quite good. She just happened to be in the wrong place at the wrong time and was never really given a fair shake until Big Finish went in and proved to everyone how utterly brilliant she could be....
