Senior AI Engineer - LLM Post-Training & Fine-Tuning

£130,000 - £180,000 + Benefits

Central London | Permanent | Office-Based

We're working with a rapidly growing AI company that's building its own proprietary large language models and expanding its AI Labs team.

This isn't an API integration role, prompt engineering position or RAG application development. We're looking for an engineer who has genuine experience improving foundation models through post-training and fine-tuning.

You'll be responsible for enhancing existing pre-trained models by designing and optimising fine-tuning pipelines, curating high-quality training datasets, building robust training environments and improving model performance for real-world production use cases.

Current projects span proprietary LLMs, conversational AI, agentic AI and next-generation AI systems deployed to enterprise customers at scale.

What You'll Bring

• Commercial experience with LLM post-training and fine-tuning

• Experience with SFT, RLHF, DPO, LoRA/QLoRA or similar techniques

• Strong understanding of transformer architectures

• Experience preparing, curating and formatting datasets for model training

• Strong Python and PyTorch skills

• Experience building production ML systems and training pipelines

This is an opportunity to join a well-funded AI engineering team where your work will have an immediate impact on the performance of production AI models used by enterprise customers worldwide.

Salary: £130,000 - £180,000 + Benefits

Location: Central London (5 days per week in the office)

If you're passionate about model engineering and want to work on proprietary AI systems rather than applications built on top of them, we'd love to hear from you.