Senior ai engineer

Working Hours: Full time 37.5 hours per week, from Monday to Friday

Hybrid We believe that through collaboration and connection with our colleagues we can achieve great things. Our hybrid working approach allows our people to work both in the office and at home, providing the flexibility and resources you need to succeed in your role. We don't require you to be in on specific days; instead, we ask people to come into the office 2-3 days each week. You should work with your line manager to understand what their expectations are for you, your specific role and your team.

Job Description

As Senior AI Engineer you will be the technical practitioner within the AI engineering function, leading complex technical delivery of production‑grade AI applications whilst mentoring and directing the engineering team.

You will be building AI applications that work at scale: designing and implementing retrieval‑augmented generation systems, agent workflows, automation tools, and prompt engineering patterns. Partnering closely with the AI Product Manager (who defines requirements and prioritisation), whilst collaborating with Data Science and ML Engineering functions on model integration.

• Lead technical delivery of complex AI application projects from architecture through production deployment
• Design and build production‑grade AI applications including RAG systems, agent frameworks, intelligent automation tools, and decision‑support workflows
• Establish and maintain application‑level patterns around prompt engineering, guardrails, human‑in‑the‑loop workflows, and content filtering
• Mentor and provide technical guidance to AI Engineers, supporting their growth and capability development
• Evaluate emerging AI technologies, frameworks, and architectural patterns for practical applicability within the organisation
• Ensure non‑functional requirements are met across AI applications: latency, cost‑per‑interaction, safety, content filtering, accessibility, and graceful degradation
• Collaborate with enterprise architecture to maintain alignment with organisational standards and constraints
• Manage technical debt pragmatically, making informed recommendations on build‑versus‑integrate‑versus‑buy decisions
• Contribute to governance, compliance, and risk management for AI product releases
• Drive code quality standards, testing practices, and engineering discipline within the AI engineering function

Qualifications

Job Requirements, Knowledge & Experience

• Degree in computer science, software engineering, or related discipline (or equivalent professional experience demonstrating equivalent knowledge).
• Proven track record building AI‑powered applications in production environments at scale.
• Hands‑on experience with large language models, foundation models, and modern AI application frameworks (LangChain, Semantic Kernel, or equivalent).
• Practical experience designing and implementing RAG architectures, vector databases, embedding strategies, and retrieval optimisation.

Benefits

We care about our people’s success by offering great pay, bonuses, up to 28 days off plus bank holidays, and paid time for charity work. You can personalise our benefits for you and your family, like discounts, vouchers, a pension plan and loads more. We help with your career through our amazing learning tools and top‑notch parental leave policies.

Legal & Compliance

We are regulated by the Financial Conduct Authority and all offers of employment for this role are subject to background checks, including criminal (DBS) and financial checks to meet the regulator’s standards.

We believe everyone should have the opportunity to interview for a role that matches their skills. In collaboration with our Talent, Diversity & Inclusion teams and our employee‑led DEI Networks, we identified a range of reasonable adjustments to help you feel comfortable and perform at your best self during the interview process. If you require any reasonable adjustments or have an accessibility request as part of your recruitment journey, for example, extended time or breaks in between online assessments, a sign language interpreter, or assistive technology, please contact your recruiter directly or email jobs@three.co.uk for guidance.

Closing Date: 4th July 2026