The role described is that of a Change Manager. This position is specifically responsible for controlling the lifecycle of all changes, enabling beneficial changes to be made with minimum disruption to services. The key phrases "changing fast" and the need to guide the process in a "controlled manner" directly point to the core function of Change Management. The Change Manager ensures that standardized methods and procedures are used for the efficient and prompt handling of all changes to minimize the impact of change-related incidents upon service quality.

A. Risk Manager: This role focuses on identifying, assessing, and mitigating potential risks across the organization, not specifically managing the end-to-end change implementation process.

B. Service Level Manager: This role is responsible for negotiating and managing Service Level Agreements (SLAs) to ensure that IT service delivery meets agreed-upon targets.

C. Business Relationship Manager: This role focuses on maintaining a positive relationship between the service provider and the business, identifying business needs, and ensuring service value.

1. AXELOS, ITIL® Foundation, ITIL 4 Edition. TSO (The Stationery Office), 2019.

Section 5.2.4, "Change enablement": The purpose of this practice is "to maximize the number of successful service and product changes by ensuring that risks have been properly assessed, authorizing changes to proceed, and managing the change schedule." The Change Manager is the key role facilitating this controlled process.

2. AXELOS, ITIL® Service Transition (2011 Edition). TSO (The Stationery Office), 2011.

Section 4.2.5.1, "Change Manager": This section explicitly defines the role: "The change manager is responsible for the overall process and will chair the CAB... The change manager will also review all implemented changes to ensure that they have met their objectives." This confirms the role's responsibility for guiding the process in a controlled manner.

3. University of Washington, IT Service Management Implementation - Roles and Responsibilities.

In its definition of ITSM roles, the Change Manager is described as the individual who "Minimizes the risk and impact of changes to the IT environment... Ensures that changes are properly approved and implemented without impacting services." This aligns directly with the requirements stated in the question.