Data Scientist - NLP in Westminster

M+C Saatchi World Services are looking for a Data Scientist specialising in NLP. In this role, you will design, build, and scale production‐grade language systems that transform how our products understand, retrieve, and generate text. You will work closely with engineering, product, and operational stakeholders to translate business goals into technical solutions, whilst shaping the overall direction of our AI capabilities. This is a full‐time role, based in London on a hybrid basis (2–3 days per week in the office).

About the Role: This is an applied, highly technical role focused on leveraging frontier LLM services (OpenAI, Anthropic, etc.) as well as locally deployed models to solve real business problems. You will architect intelligent systems, implement robust NLP pipelines, and deploy solutions that are reliable, secure, and performant at scale.

What you’ll do:

• Design and build LLM‐powered applications using third‐party APIs (OpenAI, Anthropic, etc.).
• Develop RAG (retrieval‐augmented generation) systems including document ingestion, chunking strategies, and vector search infrastructure.
• Implement advanced prompt‐engineering patterns, evaluation frameworks, and output‐reliability mechanisms.
• Build NLP pipelines for text classification, entity extraction, semantic search, summarisation, and document understanding.
• Develop agentic workflows and tool‐use systems for complex multi‐step tasks.
• Optimise for cost, latency, reliability, and model selection across LLM providers and configurations.
• Collaborate with product and engineering teams to translate business requirements into robust technical solutions.
• Build monitoring, observability, and evaluation systems for LLM applications in production.

About You: What you bring (knowledge, expertise, experience, and skills):

• Solid experience in applied NLP or machine learning roles.
• Strong proficiency in Python and experience building production systems.
• Hands‐on experience with LLM APIs (OpenAI, Anthropic, or similar).
• Experience building RAG systems including loaders, text splitting, embedding models, and vector stores.
• Solid understanding of NLP fundamentals: embeddings, semantic similarity, text classification, and evaluation.
• Experience with prompt engineering and structured output parsing.
• Strong software engineering fundamentals: version control, testing, code review, documentation.
• Experience with cloud infrastructure (AWS preferred).
• Desirable: Experience with LLM orchestration frameworks (LangChain, LlamaIndex, etc.).
• Background working with vector databases (Pinecone, Weaviate, pgvector, Chroma).
• Experience building agentic LLM workflows (tool calling, function calling, multi‐step reasoning).
• Familiarity with LLM evaluation and observability tools (LangSmith, Weights & Biases, etc.).
• Experience fine‐tuning API‐based models or working with embedding models.
• Understanding of cost‐optimisation strategies across providers and model tiers.

What You Get: A competitive salary and benefits package that includes 27 days holiday per year, pension contributions, private healthcare, discounted dental insurance, enhanced maternity/parental leave, plus a whole host of others including:

• Cultural stimulation allowance - £250 per person per year
• Half days off before bank holidays
• Emergency care days for dependants
• Up to 5 days volunteering leave per year to work for a registered charity
• Up to 10 days special emergency leave per year
• Season Ticket loan
• Payroll Giving Scheme
• Thursday drinks to unwind and socialise
• An annual Summer and Christmas party

Our commitment to Diversity and Inclusion sees us offer inclusive bank holidays. We also offer learning opportunities around D&I, targeted mentoring programmes and the opportunity to participate in several active Employee Led Networks and associated events. Finally, this role will be supported with all the necessary personal development required to set someone up for success.

About M+C Saatchi World Services: M+C Saatchi World Services is a specialist division of M+C Saatchi Group, the world's largest independent communications network. Our specialists work in office hubs across six continents, grounding our global expertise in local nuance. We offer award-winning commercial communications capabilities, which are utilized by global organizations to address the world’s most complex problems across defence, development, diplomacy, homeland and national security, law and order, health, education, and the environment. We work with clients that want to help the hardest-to-reach, hardest-to-influence audiences. This includes a range of Western Government departments, such as DOS and USAID; partner governments, including the U.K. and Australia; and prominent IGOs/NGOs such as the U.N. We are a comms agency that works on behaviour change projects typically focused on issues related to Security, Defence and Stabilization.