TL;DR:

• The Sovereign AI Unit has taken its first equity stake in Callosum, a London AI-infrastructure startup, and opened supercomputer access to six more companies.
• Backed firms receive up to 1 million GPU hours, same-day visa decisions and ten free R&D visas each — a package usually reserved for the largest tech employers.
• The announcement lands the day after UK ministers urged banks to worry about Anthropic’s Mythos model, highlighting the tension at the centre of Britain’s AI strategy: back it, and brace for it.

Technology Secretary Liz Kendall launched the Sovereign AI Unit on 16 April at self-driving firm Wayve’s London office, unveiling Callosum as the first company to receive an equity investment from the £500 million fund. A second, unnamed business has also been backed, and six startups will share access to the UK’s AI Research Resource supercomputer network.

A state-run venture capital fund

Sovereign AI is structured to behave like a venture capital firm — moving at startup pace, taking equity positions and securing a right of first refusal on follow-on rounds. The six firms receiving compute are Prima Mente (biological foundation models aimed at Alzheimer’s and Parkinson’s), Cosine, Cursive (autonomous agents, founded by Google DeepMind alumni), Doubleword, Twig Bio and Odyssey (world models). Roughly 30 further firms are in discussions.

Beyond capital, backed companies get up to 1 million GPU hours on UK supercomputing capacity, visa decisions within a working day, ten cost-free R&D visas each, and direct support on data access, early government procurement and regulatory routes. A separate £282 million R&D programme opened its first funding call for AI datasets and enabling assets.

The Mythos backdrop

Kendall framed the launch as a national bet to make Britain “an AI maker, not just an AI taker”. Speaking to reporters the same week that UK finance regulators held crisis talks over Anthropic’s Mythos model — which has found zero-day vulnerabilities in every major operating system — she urged the country to “seize” AI despite cybersecurity fears. Chancellor Rachel Reeves described a “thriving domestic AI sector” as one of her three big economic bets.

Looking forward

The test for Sovereign AI is whether equity-style involvement proves more durable than earlier UK innovation schemes, which tended to hand out grants rather than take stakes. The fund’s chair, Balderton partner James Wise, has signalled a lean toward AI safety and security companies — a stance shaped by the Mythos moment and likely to guide which of the 30 firms in discussions secure backing next.