Cosine, a London-based AI startup founded in 2022, has assembled a coalition of major British institutions, including BT, Lloyds Banking Group, NatWest, HSBC, LSEG, BAE Systems, Thales UK and Babcock, to co-design Lumen Sovereign, a frontier AI model trained entirely on UK infrastructure. The model will run on Isambard-AI, one of Europe's most powerful supercomputers, using compute awarded through the UK government's 500 million pound Sovereign AI programme, with deployment readiness targeted for the end of 2026.
Cosine was selected among the programme's first cohort of supported startups in April, receiving 500,000 GPU hours on Isambard-AI and an option for the Sovereign AI Fund's venture arm to participate in the company's next funding round. The company focuses on customers in defence, critical infrastructure and other regulated sectors, where data-handling rules can restrict the use of foreign-hosted AI tools, and says its coding models have outperformed systems from OpenAI, Anthropic, Mistral and DeepSeek on independent benchmarks for two consecutive years.
Lumen Sovereign will be developed using proprietary datasets built entirely in-house across pre-training, mid-training and post-training, rather than adapted from an existing open-source checkpoint, and deploys within a customer's own infrastructure without an internet connection or data leaving the site. Cosine co-founder and CEO Alistair Pullen framed the effort around dependency risk: Cursor and Claude Code are outstanding products, he said, but they are legally off the table the moment a customer's work touches classified infrastructure.
