there is only one word I can use to describe series 4, I'll give you a hint it begins with "S" and ends in "T", that's right SUFFICIENT it wasn't anything special but it was better than most of the other rubbish on TV at the time. The main problem I had with it was that they had already finished the story perfectly in series 3 so in series 4 they just didn't add anything on to the previous story plot. it may have well have been a completely different show. Killing off or getting rid of the entire original cast wasn't the wisest of decisions either.