Lead Knowledge Graph / Ontology Engineer

Lead Knowledge Graph / Ontology Engineer (Contract) 📍 UK (Hybrid) ⏳ Initial 6-month contract (extensions likely) 💷 £600–£700 per day (outside IR35, experience dependent) The Opportunity A UK-based organisation is embarking on a major data and AI transformation programme for 2026 and beyond. The focus is on unifying large volumes of semi-structured and unstructured data from diverse sources — including APIs, web data, documents, internal systems, and regulatory datasets — into a trusted, interconnected knowledge graph platform. This programme underpins the next generation of data-driven applications, combining ontology-based reasoning, inferencing, NLP, and explainable AI to enable richer insight, discovery, and decision-making across complex legal and regulatory domains. We are seeking a Lead Knowledge Graph / Ontology Engineer to take technical ownership of this initiative from design through to production. Key Responsibilities • Lead the design, build and deployment of entity-resolved knowledge graphs and ontologies, from concept to live environments • Embed semantic and ontology-based reasoning into business-critical systems, including explainable AI and context-aware discovery solutions • Define and maintain a standardised ontology, taxonomy and business glossary • Design and implement ETL, streaming and CDC pipelines, including entity resolution across multiple data sources • Clean, enrich and integrate structured and unstructured datasets into a coherent knowledge graph • Author and optimise complex graph queries, ensuring performance, scalability and efficiency • Develop and evaluate graph-based ML models (e.g. link prediction, anomaly detection, community detection) • Research, benchmark and recommend knowledge graph and ontology frameworks • Ensure compliance with relevant data protection and regulatory requirements (e.g. GDPR) • Apply advanced NLP / NLU techniques including NER, relationship extraction, topic modelling and summarisation • Deliver training sessions, workshops and presentations to technical and non-technical stakeholders Required Experience • Minimum 5+ years’ hands-on experience delivering production knowledge graph and ontology solutions • Strong expertise with semantic web standards and tooling, including RDF, RDFS, SKOS, OWL, SHACL, SPARQL, Apache Jena, and OWL reasoners • Experience with multiple graph databases (RDF and/or LPG), such as GraphDB, Stardog, Amazon Neptune, Neo4j, TigerGraph or ArangoDB • Proven background in entity resolution techniques (deterministic, probabilistic, blocking, etc.) • Advanced Python skills with production-grade code, including experience using libraries such as NetworkX, TensorFlow, PyTorch, spaCy, Hugging Face, Pandas, NumPy and Scikit-learn • Ability to translate complex business and regulatory requirements into structured, ontology-driven models • Solid understanding of data governance, metadata management and FAIR principles • Excellent communication skills with the ability to explain complex concepts to non-technical audiences Nice to Have • Graph visualisation and UI experience (e.g. Linkurious, Ogma) • Graph database certifications (e.g. Neo4j, Stardog) • Experience building conversational AI solutions (e.g. RASA) • Additional programming languages (Java, JavaScript, C++, etc.) Ideally this would be a hybrid (needs must worst case) arrangement so being based close to Chester would be ideal. Fundamentally, this will be remote first,