AI Engineer (Up to £220k + equity)

Oliver Bernard; Greater London; Hybrid; GBP 132,000 - 220,000; Full time

Job summary

Oliver Bernard is sourcing a Staff / Principal AI Engineer for a frontier AI platform in London. This senior IC role will own major initiatives across model improvement, post-training, RL and evaluations, delivering production-ready AI infrastructure.

The position requires hands-on ML expertise, strong Python production skills, and leadership while remaining an IC. London-based, hybrid work with equity potential is offered.

Qualifications

• Deep hands-on experience training and fine-tuning ML models.
• Strong understanding of modern ML, RL, evaluation and model optimization.
• Experience building agentic systems or AI infrastructure.

Responsibilities

• Own major AI initiatives from research question through to production.
• Lead work across post-training, fine-tuning, RL and model evaluation.
• Build agent harnesses, sandboxed execution environments and feedback systems.
• Develop training-data, synthetic-data and curation pipelines.
• Design experiments, evaluation frameworks and measurable success criteria.

Skills

ML model training & fine-tuning

Production-quality Python

RL & evaluation frameworks

AI infrastructure

Tools

Python

Job description

Staff / Principal AI Engineer, AI Platform | Up to £220k + Equity | London, Hybrid.

We’re working with a well-funded frontier AI company building the infrastructure used to train and evaluate increasingly capable AI agents.

They create interactive software environments where agents can complete tasks, receive feedback and improve through experience. The platform is already being used in real training and research workflows with leading AI labs.

They’re now scaling the core AI platform and hiring senior ICs to own major areas across model improvement, post-training, RL, evaluations and agent infrastructure.

Role

A deeply hands-on Staff / Principal position with significant technical ownership. You’ll define research and engineering direction while staying close to models, experiments and production systems.

Responsibilities

• Own major AI initiatives from research question through to production


• Lead work across post-training, fine-tuning, RL and model evaluation


• Build agent harnesses, sandboxed execution environments and feedback systems


• Develop training-data, synthetic-data and curation pipelines


• Design experiments, evaluation frameworks and measurable success criteria

Requirements

• Strong hands-on experience training, fine-tuning or post-training ML models


• Deep understanding of modern ML, RL, evaluation and model optimisation


• Experience building agentic systems or AI infrastructure


• Strong software engineering fundamentals and production-quality Python


• Track record owning technically ambiguous, high-impact projects


• Staff / Principal-level technical leadership while remaining an IC

Tech

Location

London, typically 2 days per week.

Package

Up to £220,000 base depending on experience, plus meaningful equity.