Principal/Staff Security Engineer

About Radiant Radiant is redefining how AI infrastructure is built. We design and operate AI-native infrastructure platforms engineered for sovereignty, performance, and scale — powering GPU-native workloads, multi-tenant control planes, and high-performance AI systems for the most demanding environments. We are building purpose-built AI infrastructure from powered land, to compute, to software. As we scale our operations and deploy capital into the next generation of AI infrastructure, we are looking to expand our finance team with leaders who can combine technical strength with execution excellence and are driven to build. Radiant was established by Brookfield, a leading global alternative asset manager with over US$1 trillion of assets under management across real estate, infrastructure, renewable power and transition, private equity and credit. Brookfield's global relationships, investment expertise and access to long-term institutional capital provide Radiant with a differentiated platform from which to develop, finance and operate AI infrastructure assets. This combination of entrepreneurial execution and institutional sponsorship enables Radiant to pursue large-scale GPU and AI infrastructure opportunities globally. About the Role Location: UK (occasional travel to data centre and test environments, confirm exact cadence) | Employment Type: Full-time, Permanent | Reports to: VP Information Security We're looking for a Principal/ Staff Security Engineer to join Infosec, reporting to our VP InfoSec. This is a hands-on, individual contributor role. You will need a deep, technical understanding of Kubernetes clusters, network architecture and access controls to manage our production environment. As we move toward owning and operating more of our own data centre footprint, the accuracy of our firewall policies, network access controls and technical security testing matters more than ever. This role will build our internal penetration testing capability, so testing becomes more targeted and accurate over time, working alongside our external testers rather than replacing them. You will need to work proactively across engineering teams so knowledge does not sit with one person alone. What You'll Do Security Testing & Audit: Audit firewall policies and network access controls across the estate. Conduct internal penetration testing, working alongside our external penetration testing partners. Build a penetration testing strategy and cadence that improves accuracy and coverage over time. Identify and help remediate security gaps found through testing and audit. Production Estate & Technical Depth: Build and maintain a deep, working understanding of our production environment, including Kubernetes clusters, network architecture and access controls. Investigate technical issues directly and dig into root cause, rather than relying on reported findings alone. Support the VP Infosec on controls testing across the Production Estate. Access & Environment Management: Own and maintain SSO and systems access configuration. Build and maintain penetration testing environments, including small Kubernetes clusters as needed. Maintain the tooling and infrastructure supporting security testing. Collaboration: Work proactively across engineering teams to avoid becoming a single point of knowledge or failure. Document processes, findings and configurations so knowledge is shared, not siloed. Partner with the Head of Security Operations on shared governance, risk reporting and security testing. What You'll Bring Strong Kubernetes experience, with the technical depth to investigate and resolve issues directly. Experience auditing firewall policies and network access controls. Experience conducting or coordinating penetration testing. Comfortable maintaining and operating security tooling and environments on an ongoing basis. Strong written communication skills, given the solo nature of the role. Experience operating as the sole security engineer, or within a small security team. Nice to Have Network engineering experience or strong networking fundamentals. Background in data centre environments, or related infrastructure environments. Experience with AI security specifically. Exposure to compliance frameworks such as ISO 27001 or SOC 2, and an understanding of how technical controls map to audit evidence. Why Join Radiant Build Radiant's internal penetration testing capability at a moment when our security and compliance obligations are scaling fast, as a Brookfield portfolio company moving into owned data centre operations. Work directly with our VP Infosec and Head of Security Operations, protecting both our corporate and production estates. Be part of a team whose work protects the infrastructure powering sovereign and enterprise AI deployments globally. Develop your career in a Brookfield backed company with resources, mentorship and genuine growth opportunities.