Security Lead – Member of Technical Staff

About the role

Callosum’s security lead will own the design and assurance of security across a diverse set of products – from public APIs to on‑premise, air‑gapped compute clusters. You will translate customer and deployment requirements into concrete technical expectations, demonstrate guarantees in practice, and build the team that protects the platform.

Key responsibilities

• Define security architecture and requirements for APIs, orchestration stack, agentic systems and physical infrastructure.
• Translate complex security requirements into engineering work, measurable guarantees and verifiable evidence.
• Lead security assurance for sensitive deployments from initial requirements through technical review and approval.
• Build and lead the security team covering architecture, threat modelling, adversarial evaluation, incident response and operations.

Required profile

• Hands‑on experience owning demanding security assurance or sensitive deployment processes end‑to‑end.
• Strong technical foundation in infrastructure or security engineering with the ability to challenge architectural decisions.
• Proven experience securing sovereign, on‑premise, air‑gapped or multi‑tenant high‑assurance environments.
• Track record of building and leading security teams, balancing risk, prioritisation and engineering trade‑offs.

Required skills

• Security architecture
• Threat modelling
• Adversarial evaluation
• Incident response

What we offer

• Competitive salary based on skills and experience
• Equity and ownership
• Private healthcare
• Visa sponsorship and relocation support
• On‑site work in our London office with inclusive workplace culture