Principal Systems Engineer – Defence. Requires SC Clearance to start and DV eligibility. Location - Berkshire 5 days per week. Salary – Competitive DoE. We’re supporting a leading organisation operating at the forefront of defence and secure systems engineering, looking to appoint an experienced Principal Systems Engineer to take a key leadership role across complex, high-impact programmes.This is an opportunity to work on mission-critical systems in a security-sensitive environment, providing technical leadership across the full systems lifecycle while guiding multidisciplinary engineering teams.The Role• Lead the development, integration and delivery of complex systems across the full lifecycle• Provide technical oversight and assurance, ensuring solutions meet stakeholder, safety and security requirements• Manage and mentor multidisciplinary engineering teams• Own and review requirements, architecture and technical documentation• Ensure compliance with relevant industry and engineering standardsEssential Skills & Experience• Extensive experience in systems engineering across the full lifecycle• Strong working knowledge of requirements management and modelling tools (e.g. DOORS, UML, SysML, Enterprise Architect)• Proven ability to produce and review high-quality technical documentation• Demonstrable leadership and team management experience• Familiarity with industry standards such as ISO 15288, IEEE and IECDesirable• INCOSE certification (ASEP / CSEP)• Background in defence, aerospace or other safety- or security-critical sectors• Knowledge of security frameworks and standards, including NCSC requirementsEducation & Background• Degree in Engineering, Mathematics, Physics or a related discipline• Significant industry experience delivering complex systems, ideally within secure environmentsAdditional Requirements• Eligibility for DV security clearance• Willingness to travel within the UK• Full UK driving licence