TL;DR

The Cabinet Office has commissioned an urgent estimate of what it would cost Britain if its businesses were shut out of the newest AI models. The trigger was a June White House directive that briefly stripped non-US users of Anthropic’s Fable 5. Officials expect to report back within weeks.

What Whitehall asked for

Ministers want two numbers. The first is economic: what UK firms would forfeit by waiting weeks, or longer, for capabilities their competitors already had. The second is security: whether attackers overseas, running a model British defenders cannot, could locate and exploit software flaws before anyone here has patched them.

The work sits with the business and science department at the Cabinet Office’s request. Separately, the Home Office has been reviewing how far AI has spread into criminal method.

One government figure put the commercial case plainly: “When a new AI model is launched, all businesses are immediately looking at how to best use and exploit it. For the UK to be left behind by not having access — even for a couple of weeks — would cause a hit to the economy.”

Why June rattled the security establishment

Donald Trump’s directive that non-US nationals be cut off from Fable 5 caused alarm inside the National Security Secretariat. Anthropic’s answer was to pull the model everywhere rather than sort users by passport, then restore it globally.

The NCSC’s former chief executive, Ciaran Martin, now an Oxford professor, reads that outcome as partly reassuring, calling it “slightly implausible that an American AI model would be restricted from foreigners”. His warning is broader: “The US’s ability to manipulate and leverage the whole AI stack – to try and force countries to bend to its will – could be significant.”

Chi Onwurah, who chairs the Commons committee on science, technology and innovation, wants more than an arithmetic exercise. Her committee, she said, has “repeatedly emphasised that the government needs a realistic plan to achieve sovereign capabilities in critical areas or risk having its access cut off at the whim of its partners”.

Looking forward

Britain’s answer so far has been money: £1.1bn for AI hardware, and a £500m sovereign fund that now sits behind twelve domestic companies. Neither buys a frontier model. The assessment also lands days after a draft US letter telling allies to choose between American and Chinese AI blocs. Together they describe a dependency the Treasury can now price but cannot yet replace.