FOI docs: UK police's six-month live facial recognition trial in London railway stations scanned 500K+ faces, leading to no arrests and one false-positive alert (Daniel Boffey/The Guardian)

The UK police facial recognition pilot demonstrates the risk of deploying AI at scale without clear performance thresholds: after scanning more than 500,000 faces, it cost £320,000 and nearly 100 police hours, produced no arrests, and generated a false alert. For CIOs and technology leaders, the key lesson is that surveillance and AI programs must be evaluated on measurable business outcomes, operational efficiency, and governance controls before broader rollout, or they can quickly become expensive, low-value, and reputationally risky.