AI Engineer - Frontier AI

Oliver Bernard; Greater London; Hybrid; GBP 198,000 - 242,000; Full time

Benefits offered by this job

Equity

Job summary

Oliver Bernard is seeking a Principal AI Engineer to own end-to-end efforts across model training, post-training, RL, and evaluation in London. This hands-on IC role influences technical direction and requires deep production-ready AI experience.

Location is hybrid with roughly two days onsite and a base salary up to £220,000 plus meaningful equity. You'll lead major research-engineering initiatives and own ambiguous problems from experiment to production.

Qualifications

• Must have hands-on experience with training LLMs and evaluating them.
• Proven ability to design and improve training, post-training and RL pipelines.
• Strong production-ready software engineering fundamentals, preferably Python.
• Track record of solving difficult AI problems in production in a top-tier setting.

Responsibilities

• Lead major AI and research-engineering initiatives end to end.
• Build and improve training, fine-tuning and post-training pipelines.
• Develop evaluation systems, agent harnesses and feedback loops.
• Own technically ambiguous problems from experimentation through to production.
• Set technical direction while remaining close to code and models.

Skills

LLM training

Post-training pipelines

Reinforcement learning

Evaluation systems

Python

Software engineering

Education

CS/ML/Math degree

Tools

Python

Job description

Principal AI Engineer | Up to £220k + Equity | London, Hybrid

We’re working with a well-funded frontier AI company building the systems used to train, evaluate and improve advanced AI agents.

They’re hiring a Principal AI Engineer to take ownership across model training, post-training, RL, evaluation and agent infrastructure. This is a hands, on IC role with real influence over technical direction.

Responsibilities

• Lead major AI and research-engineering initiatives end to end
• Build and improve training, fine-tuning and post-training pipelines
• Develop evaluation systems, agent harnesses and feedback loops
• Own technically ambiguous problems from experimentation through to production
• Set technical direction while remaining close to code and models

Requirements

• Strong experience with LLM training, post-training, RL or evaluation
• Excellent software engineering fundamentals, ideally Python
• Track record of solving difficult AI problems in production
• Experience within a top-tier AI lab, technology company or high-bar startup
• Strong academic background in Computer Science, ML, Mathematics or a related STEM field
• Evidence of operating at Principal or equivalent senior IC level

Location

London, typically 2 days per week onsite.

Package

Up to £220,000 base + meaningful equity.