This research project investigates the role and importance of line managers and leaders in employee development, using Marks & Spencer as a case study. The study aims to understand the strategies employed by leaders and managers for employee growth and the challenges they encounter during the process. It explores the concept and significance of employee development, analyzes specific strategies used at Marks & Spencer such as encouraging recognition, on-the-job training, and job rotation, and examines challenges like increasing costs, employee conflict, resistance to change, and ineffective communication. The research employs a positivism philosophy, deductive approach, and quantitative methods, utilizing questionnaires to gather primary data. The findings highlight the crucial role of line managers and leaders in guiding and motivating employees, managing performance, and implementing strategies for organizational success. The report concludes with recommendations for addressing the identified challenges and suggests areas for further research.