To put that in real-world perspective, the average daily transaction volume for a mid-sized US grocery store (I realize this isn't the US but don't have similar data for the UK) is roughly 13,500.
This system will therefore flag, on average, 2.7 potentially life-destroying false accusations of shoplifting per day per store.
And spare us the "human review" defense, anyone who has ever worked in retail knows that you either obey the computer or find a new job. There is zero tolerance for employee discretion when it comes to safety, financial, or legal issues.