Staff AI Engineer - Stealth Start-up - London

🚀 Staff AI Engineer | Stealth Mode AI Start-up | London | Up to £200k

Oliver Bernard have partnered with a stealth-mode start-up in the AI & Research space , who are looking for a Staff AI Engineer to join the team and work on some genuinely challenging problems across LLMs, reinforcement learning and agentic systems.

This is a hands-on research + engineering role, where you’ll be involved in:

🧠 LLM training & fine-tuning – including reinforcement learning and post-training

🔄 Evaluation & feedback loops – building systems to continuously assess and optimise models

🤖 Agent development – designing and building sophisticated AI agents

🔬 AI research – exploring LLM training, RL, evaluation and optimisation techniques

💻 Software engineering – applying strong engineering fundamentals to complex AI problems

What they’re looking for:

• Strong experience working with LLMs and/or foundation models
• Deep experience with training, fine-tuning, RL or post-training
• Strong background in model evaluation and optimisation
• Experience building AI agents / agentic systems
• Excellent software engineering fundamentals
• A strong track record in AI research and solving technically complex problems

📍 London – 2 days hybrid

💰 Up to £200k

If you’re a Staff-level AI Engineer who wants to work at the intersection of cutting-edge research and production engineering, apply below for more information.

London | Stealth | Staff AI Engineer