To verify the authenticity of an appointment letter from Venitelle Hospital, UK as a Social Worker, it is recommended to reach out directly to the Human Resources department at the hospital. They will be able to confirm the legitimacy of the document and provide any additional details you may require. It is essential to ensure that all aspects of the letter align with standard practices and comply with relevant labor laws and regulations. If there are any doubts or discrepancies, seeking clarification from the HR department is the best course of action to validate the appointment letter.