lecturing one subject with other lecturer's material I have been appointed to teach one course in Artificial Intelligence in one university. The reason was that the main lecturer is involved in other duties and for that reason he could not teach one group (there are two groups actually). The thing is that this lecturer has given me all the material: slides, exercises, exams, practices, final project and so on; and he told me explicitly to follow that material.

I have been always a big fan of the freedom of teaching. I mean I believe that if two different lecturers teach course X; then it would be better if they can get two different approaches for the same topics. The Faculty academic coordinator has told me that I must follow the material exactly, because the examinations would be the same for both groups.

I wonder what to do in this situation? I am keen to take published material as a reference for a course, but not to follow all the material exactly from the other lecturer like if I were some sort of "academic monkey" (that only mimics what the other has made). I really feel frustrated about this situation and I do not know what to do.

Usually when I have gotten into this situation, in which I had to drop one group and that group has been assigned to another lecturer. I have given him/her full freedom, and only we gather around for making the practices and exams together. I really believe that is the correct way to do this things.

Any advice?

PD Some clarification points:


The other lecturer and myself be both have the same rank, I mean we both are lecturers, only difference is that the other lecturer has taught the course before and that is why he was appointed coordinator of only that course.
In academic ranks, I got more academic background in CS (two master's already done); in the other hand he is a die hard programmer programmer that has participated in programming contests, but that's it. He has only a bachelor in Information Systems.
The material handed to me is simple, but it gets to my nerves that I must stick completely to it. I mean if a student is well prepared and every teacher follows the syllabic contents; then at the end it does not matter who made the final examinations. The student should be prepare for everything (except that the course is about, for example a Java certification, and I do not teach Java, but C). The point is that is a CS related course, and for that it should relies more in the algorithmic part that on some tricky-twisty programming stuff that tough programmers know.
In Academia there is always a lot of egos involved. Do not take it personal and let your ego get in the way. As you admit, you are not the main lecturer. He is. He prepared the slides, exercises, exams, practices, final project and so on. Excellent. Less work / stress for you. It is not your time to shine. In any job (academia or not) you must learn how to play "second fiddle" if needed. And this is one of these times.

On the other hand, teaching is much more than the slides, exercises, final project or exams. It is the teacher's personality, how he is in sync with the classroom needs, how to make the students participate in the course and how to make the lesson an unforgettable experience. You can and must try to do all these, regardless of the slides you use. So you can still make all the students want to watch your lecture (instead of his) if that is what it takes to boost your ego. Although it clearly is not a competition. It is just a job. So, do it as best as you can with the tools you are given. It is really that simple.

Update. 

From the comments I see, there is too much focus on "No-one should tell how to teach...". But this is not really the point. If professor B was supposed to teach both lectures and due to a newly assigned duty he cannot, would not that be impolite / inconsiderate for the new professor (Layla) not to give her (at least) the materials and slides he uses? If someone steps in for me, I would most certainly do all the necessary work for my coleague to have the most seamless transition by alleviating some of the stress /work for preparing lectures / slides, exercises. And if I was the subsitute I would appreciate this offer. Why must egos be involved in such a process and why should anyone not accept the offer given? If this situation continues for the next semester - year, Layla should have a saying on how the lecture should be done. But for this year I do not see the point in making too much fuss over it.