How many?? Really??
"UK police are typically only able to use LFR for specific investigations and can only scan crowds for faces on a police watchlist, which is populated by around 20 million images."
Is there any context that could be added to this number?
On reading it (as a lay person) either about 1/3 of the UK population is "wanted" in some way, or we're possibly looking for every criminal from the shoplifters of Little Hadingham to the carjackers of Cape Town, the latter being unlikely to be reasonably expected as a "hit". Is it perhaps a combination of images of as yet unidentified persons from crime scenes (so possibly many images will actually relate to one person), grainy CCTV not worth using, passport photos (https://www.theregister.com/2025/08/08/uk_secretly_allows_facial_recognition/?td=readmore) or a mixture of these and/or something else? Perhaps some kind of subset is used?
I think that, if available, some explanation of the number might help inform the debate, as clearly fewer than that fraction of the population are being invited for a chat down at the station whilst out picking up their groceries. Unless the hit rate is really really poor, or they're all very good and hiding.