A Project Brief is produced to provide a full and firm foundation for the initiation of a project. This document outlines the project's objectives, scope, constraints, expected benefits, and structure of the project management team. It serves as the basis for the next process, Initiating a Project, where more detailed planning and definition of the project take place.
PRINCE2 7 Foundation handbook and official documents.

Explanation
Reference https://www.prince2primer.com/prince2-2017-risk-theme-changes/

According to the 'manage by exception' principle in PRINCE2, when any forecast indicates that tolerances are likely to be exceeded, this issue must be escalated to the project board for decision-making. This principle supports efficient use of management time by only involving them when necessary, such as when predefined thresholds are anticipated to be breached.
PRINCE2 7 Foundation handbook and documentation on the 'manage by exception' principle.

The objective of the Closing a Project process in PRINCE2 includes reviewing the performance of the project against its baseline. This ensures that all objectives have been achieved, the project has delivered the required products, and stakeholders are satisfied with the outcomes. It provides a formal closure to the project by ensuring all project work is completed and assessed. References: PRINCE2 Foundation manual, PRINCE2 official resources