Security Lead & Staff Engineer: End-to-End Assurance

Callosum; Greater London; On-site; GBP 90,000 - 150,000; Full time

Benefits offered by this job

Equity & Ownership

Private healthcare

Visa sponsorship

Relocation assistance

London office

Job summary

Callosum in London is seeking a senior Security Architect to own the security strategy across API, orchestration, and on-premise infrastructure. You will translate customer and deployment requirements into concrete technical expectations, lead security engagements, and build a high-calibre security team.

You'll work with customers, partners, and reviewers to demonstrate guarantees in practice, balancing risk, cost, and performance while guiding architecture decisions across the stack.

Qualifications

• Experience personally owning a demanding security assurance or sensitive deployment process end-to-end.
• Strong technical foundations in infrastructure or security engineering, with the depth to challenge architectural decisions.
• Experience securing sovereign, on-premise, air-gapped, multi-tenant, or other high-assurance environments.

Responsibilities

• Define security architecture and requirements across API, orchestration stack, agentic systems, and physical infrastructure.
• Translate complex security requirements into specific 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 across architecture, threat modelling, adversarial evaluation, incident response, and operations.

Skills

Security architecture

Threat modelling

Incident response

Security engineering

Team leadership

Job description

Callosum in London is seeking a senior Security Architect to own the security strategy across API, orchestration, and on-premise infrastructure. You will translate customer and deployment requirements into concrete technical expectations, lead security engagements, and build a high-calibre security team.

You'll work with customers, partners, and reviewers to demonstrate guarantees in practice, balancing risk, cost, and performance while guiding architecture decisions across the stack.