The interviewer is trying to learn more about why you've made the decision to pursue new opportunities. Discuss with the interviewer your reason for leaving your current employer, then explain what makes the role at the NHS appealing to you. Maintain a positive and professional tone; avoid complaining about your current or previous company, manager, or team, as hiring managers usually see this as a red flag. Instead, give a more general reason like "I'm looking for more opportunities for growth," "I'm ready to explore new industries and expand my skillset and experience," "I'm looking for a shorter commute, etc., "