Why is it so important to "begin with the end in mind" when planning an assurance engagement?

An internal audit function has agreed to conduct an advisory consulting engagement related to evaluating the efficiency of a process. During this engagement, an internal auditor identifies a control weakness that be material to the company. Since a consulting engagement is could between two parties—the customer and the auditor—is there any obligation to disclose this weakness to senior management and the audit committee? What are the benefits and drawbacks of an internal auditor communicating such a weakness?

Can consulting engagements be structured to also provide assurance? Why or why not?

Discuss in your own words what skills and training are most important for the internal audit function to be successful at consulting engagements?