Few people realise how many databases may include images of their face; these may be owned by data brokers, social media companies such as Facebook and Snapchat, and governments. The systems in use by Snap and the Chinese start-up Face++ don't save facial images, but map detailed points on faces and store that data instead. The FBI's latest system, as of 2017, gave it the ability to scan the images of millions of ordinary Americans collected from millions of mugshots and the driver's licence…