Last seen wearing ...

Having read the book Last Seen Wearing by Colin Dexter a couple of weeks ago, I decided to dig out the DVD and watch the adaptation for TV as portrayed in Morse.  The most striking thing about the TV version is that it bares very little resemblence to the book.  Just about everything has been changed - context, the characters and their lifestyles, the relationships between the characters, the storyline, the killer's identity.  It's a wonder that they even called it 'Last Seen Wearing'.  I really don't understand why the writer did this.  The book could have been adapted as is and it would have worked just as well, if not better than the adaptation (if one can call it adaptation).  What I do know is, it annoyed the heck out of me and the person I gave the running commentary to on what had been altered!  If I was Colin Dexter I probably would have been livid.  I'd love to hear a rationale explanation as to why so many changes were made as I really can't think of any.