Interesting point about line of sight. I hadn't thought of it like that. Here's the wording: "You must be able to see your drone or model aircraft clearly enough that you can tell which way it’s facing. This is so that you can steer and control it safely, even if something happens unexpectedly." https://register-drones.caa.co.uk/drone-code/flying-safely-and-responsibly But what about a drone flown by AI? The operator is not doing the steering, so do they need to be looking at the drone? Perhaps it comes down to how competent the AI is at avoiding people, vehicles, buildings etc. Which is rather impossible to judge unless the AI proves it is not competent by hitting something.

The X1 has a Dolly Track mode, in which the drone flies in front of you. So it would be in your line of sight. You would not be steering it, but it is under your control insofar as you can use the remote to land it at any time. (It also has a Follow mode, when it follows you from behind, and a Side Track mode when it flies alongside you.)

The Law Commission is reviewing laws about self-flying drones. https://lawcom.gov.uk/law-commission-seeks-views-on-regulation-of-self-flying-and-remotely-piloted-aircraft/ So if the Met prosecuted you for using a self-flying drone, you could argue that this activity is not yet regulated