Senior Software Engineer (C/C++) – UK Defence Programmes (SC / DV Required)
This is a senior, delivery-focused engineering role in a cleared UK defence environment—built for engineers who want to ship high-assurance software, not just talk about it.
We are hiring experienced software engineers to deliver mission-critical systems into UK defence programmes where engineering evidence matters. You will work on long-running, complex products under security, safety, and operational constraints—with the autonomy to make sound technical calls and the responsibility to stand behind them.
If you are looking for a role to “grow into seniority”, this position will feel too demanding and too exposed. We need people who can take ownership from day one in a cleared environment.
Security Clearance (Non-negotiable)
To join this programme, you’ll need to already hold active UK Security Clearance at SC or DV level. Because of the nature of the work, we’re unfortunately not able to sponsor, initiate, or wait for new clearances, so you’ll need to be able to start working in a cleared environment straight away.
Seniority expectations
This role is intended for engineers who have already operated at senior level in high-assurance environments and can lead technical delivery end-to-end.
- Senior engineers (typically 10+ years) who have owned delivery of complex software through design, implementation, verification, and integration
- Exceptional engineers (typically 7+ years) already performing at senior / technical-lead level in defence, aerospace, or other safety-critical domains, with a track record of making pragmatic trade-offs under constraint
- Contribute directly to architecture, design decisions, and trade-offs.
- Operate effectively in multi-disciplinary teams alongside systems, safety, and assurance engineers
What you will be expected to do
- Take technical ownership of software delivered into regulated, high assurance environments
- Deliver robust C / C++ software that meets demanding requirements for reliability, safety, and maintainability
- Work across the full software lifecycle, including:
- requirements analysis
- system and software design
- implementation and verification
- integration and support
- Communicate clearly and precisely with technical peers and programme stakeholders
What we expect from you
- Proven experience delivering software into defence, aerospace, or safety-critical systems, ideally with exposure to assurance, certification, or safety cases
- Strong, hands-on expertise in C and/or C++ (modern practices, memory/ownership discipline, performance-aware design, and debugging on real targets)
- Experience with embedded and/or Linux-based systems (e.g., RTOS, bare metal, Embedded Linux), including integration constraints and hardware interfaces
- Confidence with toolchains, build systems, and release workflows (e.g., cross-compiling, CMake and equivalents, linkers, packaging, and reproducible builds)
- Evidence-driven engineering: familiarity with coding standards, static analysis, and code review discipline (e.g., MISRA/CERT-style rulesets, treating warnings as actionable)
- Strong testing mindset: unit/integration testing and automation, working effectively within CI pipelines (e.g., Jenkins/GitLab CI or similar)
- Comfortable working with requirements, traceability, and verification evidence(e.g., DOORS or similar tools/processes)
- Security-aware mindset: understanding of secure coding and threat-driven thinkingappropriate to defence environments
- Able to make and stand behind engineering decisions and trade-offs, and communicate them clearly to technical peers and programme stakeholders
- Professional maturity to operate effectively in regulated, high-assurance environmentswhere process exists for a reason and delivery still matters
What this role offers
- Work on real UK defence programmes—software that is deployed, used, and relied upon
- Long-term, technically demanding work where engineering quality and evidence genuinely matter—not just speed of delivery
- An environment that trusts senior engineers with autonomy, responsibility, and influence over design decisions, ways of working, and technical standards
- Flexible working where possible, balanced with the realities of on-site work in cleared environments
- Competitive compensation and benefits aligned to the market for senior, cleared engineers (details discussed transparently during the process)
Important notes
- No visa sponsorship is available for this role
- Adjustments can be made to the recruitment process where required
Critical Software is proud to be a Benefit Corporation. A Benefit Corporation differs from a standard corporation (C-Corporation): it is a for-profit business entity, legally defined in the US and other jurisdictions, whose goals include positive impact on society, workers, the community, and the environment, alongside profit.
We are an equal opportunity workplace and committed to ensuring candidates with disabilities or neurodevelopmental conditions can demonstrate their skills fully. Where needed, we can make adjustments to the recruitment process—please let us know what support you require.
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Top Skills
What We Do
At Critical Software, we believe our people are the core of who we are. Their talent, diversity, and ability to go beyond expectations shape everything we do. Working at Critical is about being part of a community built on purpose, values, and collaboration. Our commitment to engineering excellence makes us a trusted partner for some of the world’s leading companies in Aerospace, Railway, Medical Systems, Energy, Finance, and many more. We believe that technology is nothing without a passion to use it for good. That’s why we engineer change, helping to build a better and safer world through trusted and transformative technologies. Since 1998, we’ve helped companies in global industries like aerospace, transport, energy, healthcare and finance. Across the world, people and organisations depend on what we do. And we like that. Because it means that technology isn’t just our business. It’s our chance to help change the world. More than a company, we are a community. Our togetherness, culture and values are the foundations of who we are and what we do. We are proud to hold Benefit Corporation status, reflecting our commitment to sustainability, transparency, and business for good. We’re also one of only a few tech companies in the world to have both our waterfall and agile software development processes rated at CMMI® Level 5. Just as important as our technical expertise is our strong company culture, which guides us in everything we do. We’re recruiting for all of our locations right now and, if you’d like to find out more, please take a look at the careers section of our website.
