A “project manager” is what most project BoKs consider as necessary to lead a project. Nevertheless this is one possibility among many. Most frequently, the company high level management wants to keep a strong hand on projects, so putting their project managers into uncertain positions.
Moreover, this strategy has proven that it challenges negatively the project performance (= how well the project is driven) against the performance of the product of the project, since the project performance can be improved by rejecting some innovative solutions comprising risks, which could otherwise benefit the product.
Alternative methods to the “project manager” can be found by means of the tool described here.