Principal Mechanical Design Engineer We are looking for experienced Principal Mechanical Design Engineers to join a growing Mechanical Engineering function with opportunities across the full product life cycle. This includes everything from early concept development and detailed design through to qualification, production support, and in-service improvements. In these senior roles, you will take ownership of mechanical design activities for complex systems, working closely with specialists across engineering, manufacturing, quality, and supply chain. You''ll be responsible for raising design maturity, providing technical direction, and acting as a key interface for internal teams and external partners. Salary: From £50,000 depending on experienceLocation: Stevenage (relocation support may be available)Hybrid Working: Typically 2 to 3 days on site each week, depending on project needsSecurity Requirements: You must be a British citizen or a dual UK national able to meet the criteria for this role The Role This opportunity will allow you to lead significant mechanical design packages on high-integrity engineering projects, influencing design decisions across all stages of development. You will help ensure that solutions satisfy performance, safety, cost and schedule expectations, while also contributing to continuous improvement of design methods, processes and tools. These positions offer long-term development potential, including pathways into advanced technical leadership or