Principal Software Engineer

Matchtech are working closely with a UK defence technology organisation delivering secure communications and cyber solutions used in mission-critical environments. Their teams build high-assurance cryptographic and key management capabilities that enable the confidential exchange of sensitive information for customers operating across tactical and strategic settings.

If you enjoy solving hard engineering problems where security, reliability, and real-world outcomes matter, this is a good fit.
Important information

Clearance
Due to the nature of the work, applicants will need to meet UK security clearance eligibility requirements (including UK residency criteria).
DV clearance is required (you must be eligible and willing to obtain and maintain DV; SC is typically required first).
Working arrangement
Fully onsite: please only apply if you can work onsite in Maidenhead The role
You'll provide technical leadership in a software engineering team (typically 5 to 20 engineers) delivering multiple concurrent R&D and production programmes. The focus is on embedded and/or application software in secure environments, with end-to-end ownership across the software lifecycle (requirements through design, implementation, test, verification, deployment and support).

You may also have line management responsibility (up to c. 5 engineers, depending on team structure).
Key responsibilities

Lead the architecture, design, development, documentation, and testing of embedded and/or application software.
Derive software requirements and architecture from higher-level system requirements and design artefacts.
Apply object-oriented design principles to support reuse and integration with test frameworks.
Produce and maintain designs/models using tools such as UML/SysML approaches and modelling environments (e.g., Enterprise Architect-type tooling).
Promote strong engineering practice: secure development, coding standards, static/runtime analysis, CI, and automated testing.
Estimate effort and deliver against agreed cost/schedule commitments.
Contribute to improving tools, processes, and engineering standards across the wider software community.
Provide technical input to bids/proposals, including estimates and risk assessments.
Mentor engineers; lead reviews and sign-off of significant technical deliverables.
Maintain information security in line with government and programme requirements. Essential skills and experience

Degree in an engineering/science/maths discipline (or equivalent practical experience).
Strong experience in at least one of the following:
Embedded product development (bare-metal and/or RTOS, e.g., ThreadX/QNX or similar)
Embedded Linux application, kernel, and/or driver development
Strong C and C++ development background.
Solid understanding of modern software lifecycle practices (requirements, design, implementation, test/verification).

Experience with OO design, design patterns, and principles such as SOLID.
Strong testing mindset: design for test, automated test approaches, and verification. Desirable

Rust
JavaScript / Node.js / React (where relevant to tooling or supporting applications)
Communications protocols (e.g., TCP/IP)
CI/CD and automated test frameworks
Secure/defensive coding standards (e.g., MISRA exposure)
Requirements/model-based tooling exposure (e.g., DOORS-like requirements tools, UML/SysML modelling) Working pattern & benefits

Fully onsite role in Maidenhead.
Competitive package including bonus, pension, private medical, strong holiday allowance, and security allowance (where applicable and dependent on clearance held)